Updated styleguide js section & initialisers.

• Singletons are OK too.
• Added note about using strict.
• Use GOVUK namespace for everything.

Also updated GOVUK.init to properly handle singleton initialisation.
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