Include course price in course_about template context if either the ecommerce service is enabled or shoppingcart is enabled

* mattdrayer: Add bulk checkout link to course views
* asadiqbal08: MAYN-225 replace the "Verify Now" button by the "Go to Dashboard" button in case of themed sites.
* mattdrayer: Add bulk_sku check in courseware.views

add test case for discussion_id already set in XML

By default, disable all caching in tests, to preserve test independence.
In order to enable caching, inherit from CacheSetupMixin, and specify
which cache configuration is needed.

[EV-32]

MA-2189

More accurately, this creates a 4th shard because the
last shard is always the default.

MA-2305

TEST_DATA_MIXED_MODULESTORE
Remove these test mixed modulestores:
TEST_DATA_MIXED_TOY_MODULESTORE
TEST_DATA_MIXED_CLOSED_MODULESTORE
TEST_DATA_MIXED_GRADED_MODULESTORE

Before this commit, roughly half the save_state AJAX calls for the
VideoModule were done at load time, in order to send information about
YouTube availability (the value for which was almost always true).

This commit sends the value for what the LMS already thinks YouTube
availability is for this user, so that the AJAX callback is only
used in the case where the client side sees something different.

[PERF-262]

More accurately, this creates a 4th shard because the
last shard is always the default.

MA-2305

The verification workflow assumes that all verified courses will have a
price. Free verified course modes cause a 404 when the user attempts to
enroll or upgrade.