[BD-2] [BB-2612]: Add ADR to define LTI Plugin architecture implementation

Removed usages of package six

Find all packages in setup.py

Merge pull request #77 from open-craft/patrick/BB-2523-add-support-for-lti-embeds-in-the-course-tabs-a

BD-02 BD-03 Add support for LTI embeds in course tabs and elsewhere

Include new packages in distribution

Renamed module to avoid import confusion

Removed deprecated future imports

[BD-2] BB-2365: Merge LTI 1.3 support to master. 

k# Please enter the commit message for your changes. Lines starting

Also fixes a few untreated exceptions and remove unused variables.

Signed-off-by: Giovanni Cimolin da Silva <giovannicimolin@gmail.com>

Signed-off-by: Giovanni Cimolin da Silva <giovannicimolin@gmail.com>

This commit adds support for the LTI 1.3 Access token endpoint, as detailed in the IMS Security Framework.
The token is generated using the consumer's private key (stored in the XBlock) after validating the message sent by the LTI Tool using it's public key.

Signed-off-by: Giovanni Cimolin da Silva <giovannicimolin@gmail.com>

Features:
Implement LTI 1.3 launch support.
Add LTI 1.3 passthrough views as LMS plugins.

Features:
Implement LTI 1.3 launch support.
Add LTI 1.3 passthrough views as LMS plugins.

AA-167: Making icon_class dynamic for LTI

[BD-6] Compliance with OEP-18

Remove constraints.
Add classifiers.
Update setup.py install_requirements definition.
Update travis file using new requirements.
Create requirements folder.
create pip_tools, base, test and travis requirements files.
Remove old requirement files.
Create Makefile and add upgrade command.
Include requirements files generated using upgrade command.
Update openedx.yml OEPs list.