Adjust asset lookup paths when chat is enabled

When chat is enabled, we need to add the Jabber Django app's static
asset and template directories to the corresponding lookup paths.
Reverting courseware changes for chat

For embedding chat in a course, user testing shows a course tab is
preferable to the slideout thing, and simpler to implement, so this
commit reverts courseware changes.  Instead, embed chat by creating a
new course tab and setting it's HTML to look like this:

  <iframe src="/courses/COURSE_ID_HERE/chat" width="100%" height="640px"
          style="border: 1px solid #c4bfab; border-radius: 5px;"></iframe>

Conflicts:

	lms/templates/courseware/courseware.html
Merge branch 'edx-west/release-20130617-candidate' of github.com:edx/edx-platform into edx-west-release-candidate-20130617