Feature/halogenandtoast/multiple textbooks

MAnage askbot images

Fix bug preventing comments from being in course.xml

Feature/victor/strip metadata

* course roots live in roots/{url_name}.xml
   - one is linked from course.xml

* policies live in policies/url_name.json
  - loaded based on course url_name

* Updated to pass policy through into xml parsing, so it takes effect
  before descriptor constructors are called.

* Update toy test course to new structure, fix up tests

* the former does a fallback if metadata['display_name'] isn't set.

Added styles to grade out the top and bottom of the sidebar border and f...

Added styles to grade out the top and bottom of the sidebar border and fixed spacing with the video and the sequence nav

Kimth/xqueue callback blocking

New wiki installed from pip

Feature/bridger/new wiki

capa problem answers may have static urls - needs replace_urls

Don't display 'None points' on problem rendering

Fix all of askbots style