* uses xml modulestore, and new error_handler hook

* no more __xmltree.

* create split_to_file() function
* chapters, html, problems always split
* course never split
* others based on size of subtree for now

* add error_handler member to DescriptorSystem
* call it where import errors happen
* also includes some refactoring in xml.py
* some more line length and docstring cleanups

* no functionality changed in this commit.

Add optional hide_from_toc attribute to XML elements

Kimth/lms coderesponse

Adding the ability for javascript from problems to execute more intelligently

Adding the ability for javascript from problems to execute more intelligently; for example, errors from javascript included in the returned html will show up in the console when using this mechanism.

Compiling coffee files in course data directories on startup.

Add field-error class to field with issues.

Add optional hide_from_toc attribute to XML elements to support Tutorials (which don't show up in the navigation).

* We do not want to disable existing loggers when setting up our own

Conflicts:
	common/djangoapps/student/views.py

Hotfix changes