Fixed subscription deletion

Added welcome Jumbotron with some nice info/links

Some work on start page

Added feedback_stage_for_user to feedback serializer

This field will contain the feedback stage of the subscription for which the requesting user has created this feedback. This is needed to correctly give the choice to set the final attribute in the frontend.

Fix final checkbox frontend

Fix disappearing names in feedback list

Solution Syntax highlighting

* This means a 2x - 10x performace boost especially for the student
  and the feedback endpoint

Student names in Subscription list for reviewer

Short polling on orig Feedback

Refresh button student list

FeedbackComment visiblity indication

SubscriptionEnded page

Right side of student overview is sticky

Statistics overview

Implemented Feedback History Table incl. search

Side Note: When searching the table, should the resulting filtered arr be <= than size 10 all those submissions will be prefetched if not already present and the user is able to instantanously view the submission. NICE!

Added Tests and sticky beahvior for feedback hist

Inactive subscriptions are shown

Added subscription refresh button

Fixed jwt refresh and auto logout

Added feedback link

Visual cue of final status in student overview

Correct Student for reviewer

* Reviewer feedback cannot be edited by tutors (despite assignments)
* Tutors can always edit feedback for which they have an assignment
* Reviewer is allowed to change anything anytime

Impplemented skip functionality when correcting

Subscriptions are now deletable

Added tqdm to requierements

Changed jwt auth endpoints

`/api-token-auth/` to `/api/get-token/`
`/api-token-refresh/` to `/api/refresh-token/`

Added student list page

Added submission serializer for student list view

Bare student list view is now implemented for the reviewer
He is able to view a searchable and sortable list of all students in the left pane of the window and their submissions on the right side

Fixed /?#/ bug on login page

Added `feedback_created`/`feedback_validated` counts to TutorSerializer

Added basic tutor overview

Added student overview help card

When going to the student overview page, a help card is shown on the right side which is replaced when viewing a submission

* Also restructured the converter script so it handles
  mixed (gap and source code) export files as well
* Added a sad hack that enables using a base url

* Also made minor modifications to assignment endpoint

* 'submission_pk' -> 'submission' on AssignmentSerializer
* subscription now uniformly use the private key of a model
  that they want to receive submissions from
* introduced remaining and available fields on subscription
* query key and type are now checked

* It is now possible to 'deactivate subscriptions via the delete
  http verb
* This is not exactly what was specified in #92 but should achieve
  the same result. Instead of introducing a depleted field,
  subscriptions can distinguish if they are fully depleted or just
  temporarily. The method does not involve any overhead.
* Refactorings in the subscription model to increase readability
* Creating a subscription does not have side effects (creates no
  assignment)

Other minor changes

* Assignments are now implicitly checked if feedback is created
* using the assignment endpoint to create subscriptions instead of
  subscription endpoint

Closes #93 and #92.

Also cleaned up the subscription code considerably

Routing is ow dynmacilly handled by selector components. E.g. the LayoutSelector will render as the correct Layout depending on the logged in users role. This allows to simply route to e.g. '/home/ and the StartPageSelector will determine if StudentPage or TutorStartPage should be displayed.

* Added more tests for feedback view

* Now each view is included in one file that are held in the
  package views instead of using one big file

* Did the same this for serializers

* Now using ListSerializer to implement the custom behaviour

* Also refactored the feedback serializers and models and
  removed the FeedbackLine model

* The serializers are simpler now

* Renamed 'is_final' on FeedbackComment to 'visible_to_student'

See #90 for Problem with ExamType subscriptions

Fixed reverse query bug in Subscription model
Fixed bug in subscription view resulting in uncaught exception
Creating a subscription with a query/key/stage combination for which no assignments were available would result in an uncaught SubscriptionEnded exception and a 500 response to the client. Instead an error message with the status code 410_GONE is now sent.

Fixed reverse query bug in Subscription model

chnaged
type_query_mapper = {
	...
        SUBMISSION_TYPE_QUERY: 'type__title',
    }

to
type_query_mapper = {
        SUBMISSION_TYPE_QUERY: 'type__name',
    }

Refactored serializer id fields and camelCase names

To provide a uniform api and to save us from further work i've refactored the existing fields that used
camelCase names to use the names specified in the models (which are kebab-case).
Also everywhere where id's (whether normal or uuid ones) have been included in the serializers, the field names have been changed to 'pk' or '<model>_pk'. Pk will always link to the primary key of the model and will save us great pain should we decide to convert the pk's of more models to uuid's. Also we won't have to remebre a bunch of different ways of referring to the id for the frontend, it's always pk.
I also included the pk field in all modelserializers since this will be necessary for the frontend state management.

Frontend now expects pk fields and snake_case

Solution is highlighted / Desc. HTML is rendered

Frontend test is only manually run

Added vue-notification library

Inactivity detection preperly implementd

Client inactivity is now properly detected. A vuex plugin is used to store the time of the last commited mutation. This roughly equals the last user interaction.
If the users session is expired he will be redirected to the login page. Before that a dialog is displayed notifieng the user that they are about to be logged out.

Added created / of_tutor info to feedback comment

* Tests can now be executed from the importer
* All jobs run fine and produce correct results