Add acceptance tests of the annotatable module [LMS-1638]
Don't create more factory subclasses, just absorb the classes directly
Allow acceptance test problem functions to work without hardcoded course name
Add acceptance tests of the conditional module [LMS-1639]
Make conditional module and poll modules a little easier to understand
Add acceptance test of the Graphical Slider Tool [LMS-1641]
Add acceptance tests of capa image input
Add handler_url usable by descriptors

[LMS-1614]