* add module_from_xml param to I4xSystem
* use it to implement xmodule.get_children()
* fix a few comments here and there
* Render-time progress display for seq and vertical modules.
  - Computes fraction of subproblems done.
* Pass problem state back to js during ajax calls.
* general cleanup in capa_module.py
* add progress_changed and progress fields to json returned from each ajax handler

* Coffeescript changes to hook up sequence tracking of problem progress

* net result: sequence 'a' tags now have a progress class
* properly set css class on initial load
* fire event when progress changes after ajax calls
* also save state in 'progress' property of problems-wrapper tag
* event handler finds those tags, computes updated progress

Update jQuery and jQuery-UI to latest version

Rapid merge procedure

CMS Beginnings

Conflicts:
	rakefile
	requirements.txt

put lambda function back in, as requested during code review

Small cleanups in response to Calen + Piotr's comments

Courseware can have same random seed in multiple problems for exam. 

Add video volume control to video player

Victor/render path cleanup

Add categories and XModuleDescriptors for all module types that are used at the top level of a course

* Refactor index() so that it makes sense to me and hopefully others :)
* Rename preloaded cache of student modules to student_module_cache
* Fix line length and whitespace throughout
* add docstrings and other comments
* a few behavior-preserving tweaks to the code to make it clearer.
* Separate codepaths for with-module and without-module in index view
* Remove default chapter + section, since they don't exist anyway in course.xml

Create Calculator and Feedback form on every page