Will/fix acceptance tests

This fixes the failures due to the following changes:

1) Video and Discussion components in Studio no longer show a list of templates with one "default" item; they automatically add the default.

2) The Latex editor test was selecting the text in "section.problem", which included a span tag containing the text of the "show answer" button.  The fix uses a more specific CSS selector.

There is still one test failing which appears to be a bug in Studio checklists.  @jnater has submitted the bug report to the Studio team.

Reviewer: @jzoldak