reading WIKI_ENABLED from env.json

Problem previewing in the CMS

adding enabled features to aws.py

Eagerly load all modules when reading the course from xml, so that users who are already on a problem page can check their answers

Move vendor javascript into common/static/js/vendor, so that they can be shared between the CMS and LMS, and create an html template that includes all of the vendor js needed for the courseware

* Note: This doesn't run yet
* add config file for lms on mongo
* Some comment additions and cleanups

Get the video module pointing to the correct static files directory, without relying on get_html replacement

Split out code to replace /static urls in get_html into a separate module so that it can be used in CMS previews

Uniquify js fragments pulled from XModules, and load both XModuleDescriptor and XModule js into the cms