Got profile page working again. The grader for each course is now defined in the data dir as grading_policy.json.

* add course and org to full/course.xml
* fix error path in clean_xml script
* commit rakefile change needed by c5334f150c

* log errors, but don't fail

* new env file to run integration tests with mongo backend
  - needs askbot to get db in the right state
  - needs wiki to load pages successfully
  - not using migrations to make it run faster
* import test courses, check that each page loads without erroring.
* fix NonePointerException in index view to make tests pass
* misc formatting cleanups

* rename slug->url_name
* rename name->display_name
* docstring cleanups
* comments :)

* add fix for the file export code--remove tag tail and text,
  not just the children.

* More tests for mongo modulestore, including tweaks to test files
* add location_to_id method to CourseDescriptors
* Implement path_to_location method in mongo.py
  - TODO: does not handle position in sequences yet.
* fix bug in jump_to view.

* Clean up test data for simple, toy courses
* clean up test_mongo.py
* write initial test for path_to_location
* hook up view to use path_to_location

Next: actually implement it :)

* fix up toy course to match current format
* fix github sync test that referred to toy course

* catch exceptions and return a 404 if course not found
* add Location.is_valid(), tests
* stub of jumpto/ view.

In response to spending an hour with a strange argument passing bug that neither I nor Cale could figure out.

* pass all arguments explicitly
* pass arguments in a consistent order between classes

* 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.

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.

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