DocumentCollectionGroup supports set_document_ids_in_order!.  Also updated some tests to prove that document scopes order by ordering.
Admin can reorder and assign groups of documents in a collection by drag-dropping.
document list row shows move cursor
Documents in a collection group display in correct order in admin suite.
repairing rebase mistake
Refactored document_group_ordering.js to use constructor style and camel naming scheme
DocumentGroupOrdering follows js style guide.

Refactored DocumentGroupOrdering to follow the js styleguide
and to be a test case.
Semicolon/style tidy up for doc group ordering.
Merge pull request #953 from alphagov/ordering-for-document-collections

Ordering for document collections

https://www.pivotaltracker.com/story/show/56772878