initial commit for a mixed module store which can interoperate with both XML and Mongo module stores
add a set_modulestore_configuration to the modulestore interface. This can be used to pass in settings run the Django tier
WIP: added a get_modulestore_type. Added some unit tests. changed over the isinstance() with respect to modulestores to use this get_modulestore_type()
remove unneeded type check on the modulestore
WIP
fix tests
remove debugging logging
remove another debug logging message
update file comment on MixedModuleStore
fix missed conflict resolution
some additional comments to clarify the partially bogus course_id.
update SplitModuleStore tests to pull the course_id from the locator
fix errant conflict resolution
fix broken test after rebase
fix one more 'revision' -> 'branch' argument name change