Explicitly test the creation and deletion of every component type

The testing of all settings/text editing have been done elsewhere and should be done when testing a new component
Cleaned up code
Teach rake test_$lib to understand specific test names
Broke up long line into smaller line
Handle issues decoding requests more gracefully

Clean up some pep8/pylint violations as well
Add in the ability to handle malformed return urls.
Show a confirmation on asset delete. Fixes STUD-375.
Handle edge case when trying to aggregate progress in an empty sequence
Make url matching regex flexible to allow for browsers that munged :// into :/
Fix SessionKeyValueStore.has to use the correct indexing value when looking up data
Retrieve location from self in CustomTagDescriptor
Make request.POST be only json content when using expect_json
Standardize on get_default_time_display
Add JSON encoder for datetimes to xml export

During policy export, we want to write any python datetime objects found
as iso timestamps, rather than throwing exceptions.
Change deleted Alert to a Notification, with a timeout.
Address code review feedback
Merge pull request #290 from edx/diana/open-id-namespace

Handle issues decoding openid requests more gracefully
Handle exception with a 404
Add a test for 404 raised when requesting the profile page of a user that does not exist
Add some documentation around XModule/XModuleDescriptor initialization.