Make the id property available on both modules and descriptors, and make it a property, so that we aren't duplicating the location data

Move field definitions for XModules into mixin classes, so that descriptors and modules always have the same set of fields

readding Julian Arni's update to definition

Update course factory to reflect XBlock changes

Fix/vik/oe xblock stage2

Make sure that test-requirements.txt doesn't install versions of libraries that requirements.txt has pinned, and cache pip downloads

Advanced Settings changes.

Potentially fix xblock storage model for open ended

Make default value for format setting None, and force lms and cms to be explicit about a string default

Conflicts:
	.ruby-version
	cms/djangoapps/contentstore/tests/test_contentstore.py
	cms/djangoapps/models/settings/course_metadata.py
	common/lib/xmodule/xmodule/course_module.py
	common/lib/xmodule/xmodule/modulestore/tests/factories.py

do a bunch of pylint improvements

Feature/jkarni/folditx