Removed unused discussion-app.css, corrected utils.py to streamline icluding discussion js files
Reworked discussion assets management to work on production like environment (pipelines+nginx proxy)
Fixed broken backbone history navigation in course mode. Moved runtime-specific settings modifications to runtime callbacks.
Added discussion xblocks to course categories map
Fixed changing thread type
Copied discussion tests from upstream
Merge pull request #323 from open-craft/eugeny/discussion-backport

Production deployment fixes