* The LMS now also monkey-patches
xmodule.x_module.descriptor_global_handler_url and
xmodule.x_module.descriptor_global_local_resource_url so that we can
get LMS XBlock URLs from the DescriptorSystem. That functionality is
needed in the block transforms collect() phase for certain XModules
like Video. For instance, say we want to generate the transcripts
URLs. The collect phase is run asynchronously, without a user context.
* The URL handler monkey-patching is now done in the startup.py files
for LMS and Studio. Studio used to do this in the import of
cms/djangoapps/contentstore/views/item.py. This was mostly just
because it seemed like a sane and consistent place to put it.
* LmsHandlerUrls was removed, its handler_url and local_resource_url
methods were moved to be top level functions. The only reason that
class existed seems to be to give a place to store course_id state,
and that can now be derived from the block location.
* To avoid the Module -> Descriptor ProxyAttribute magic that we do
(which explodes with an UndefinedContext error because there is no
user involved), when examining the block's handler method in
handler_url, I made a few changes:
** Check the .__class__ to see if the handler was defined, instead of the
block itself.
** The above required me to relax the check for _is_xblock_handler on the
function, since that will no longer be defined.
90% of this goes away when we kill XModules and do the refactoring we've
wanted to do for a while.
