Remove the OIDC view from XBlock and return OIDC url directly.

* bump up the version

* update changelog

As stated by @giovannicimolin:

  Due to a recent change in `Chrome`_ and `Firefox`_
  and the way they handle cookies, it’s not possible
  to access cookies marked as ``SameSite=None`` if
  they are not also Secure.

  This is to help avoid a few CSRF attacks.

  Secure cookies are only available when the request
  is done through `HTTPS`_, which is not the case on
  the devstack.

The workaround for this behaviour is to set
``DCS_SESSION_COOKIE_SAMESITE`` from ``'Lax'``
to ``None`` in the studio container's ``devstack.py``,
when using tools such as ``ngrok``.

This commit adds a note about this to the ``README.rst``
of the repository.

.. _Chrome:: https://twitter.com/ChromiumDev/status/1293236234932846596
.. _Firefox:: https://hacks.mozilla.org/2020/08/changes-to-samesite-cookie-behavior/
.. See ``Secure`` Attribute as a reference
.. _HTTPS:: https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Set-Cookie

Also fixes a few untreated exceptions and remove unused variables.

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

Overview
---------
This pull request makes this XBlock extensible for
adding parameters to the LTI provider in addition
to the existing ones.

Why
---
A customer needs `team` and `cohort` informaiton
to be passed through the LTI channel to simplify
integration with their LTI provider. At the same
time we'd rather not fork the XBlock, so an
Open-Closed model is needed.

More Detailed Documentation
---------------------------
I've added a couple of sections to `README.rst`
to document specifying design and
configuration steps of the new LTI parameter
processors. Please check it out for more
information about the changes that this pull
request introduces.

Example Usage
-------------
I've written a package that we'll need to use for
our customer to pass some personal user
information in addition to the cohort and team
info: https://github.com/appsembler/tahoe-lti/pull/1

Omar Al-Ithawi @ Appsembler

Add context_label and context_title to LTI POST parameters; Add required requirements; add some docker devstack instructions;

updated readme

fixed link

better fix for link