fix quality violations

create child parent mapping to avoid potential performance hit when deleting items

update '_delete_item' method for draft only modules and update delete_orphans management command

fix test_courseware which fails due to invalid future date

Refactor get_parent_locations STUD-1663

This commit adds all of cms.

These keys are now objects with a limited interface, and the particular
internal representation is managed by the data storage layer (the
modulestore).

For the LMS, there should be no outward-facing changes to the system.
The keys are, for now, a change to internal representation only. For
Studio, the new serialized form of the keys is used in urls, to allow
for further migration in the future.

Co-Author: Andy Armstrong <andya@edx.org>
Co-Author: Christina Roberts <christina@edx.org>
Co-Author: David Baumgold <db@edx.org>
Co-Author: Diana Huang <dkh@edx.org>
Co-Author: Don Mitchell <dmitchell@edx.org>
Co-Author: Julia Hansbrough <julia@edx.org>
Co-Author: Nimisha Asthagiri <nasthagiri@edx.org>
Co-Author: Sarina Canelake <sarina@edx.org>

[LMS-2370]

STUD-1151

with code to translate between addressing schemes based on app
and persistence layer addressing scheme specification.

STUD-1206

Add unit tests for auth

To help fix recent bugs re orphaned discussions and
to prototype a more restful json oriented api.