Annotation Tools in Place

The purpose of this pull request is to install two major modules: (1) a
module to annotate text and (2) a module to annotate video. In either
case an instructor can declare them in advanced settings under
advanced_modules and input content (HTML in text, mp4 or YouTube videos
for video). Students will be able to highlight portions and add their
comments as well as reply to each other. There needs to be a storage
server set up per course as well as a secret token to talk with said
storage.

Changes:
1. Added test to check for the creation of a token in tests.py (along
with the rest of the tests for student/view.py)
2. Removed items in cms pertaining to annotation as this will only be
possible in the lms
3. Added more comments to firebase_token_generator.py, the test files,
students/views.py
4. Added some internationalization stuff to textannotation.html and
videoannotation.html. I need some help with doing it in javascript, but
the html is covered.