Implement ViewRevisionsResource with accompanying test
Rename all *History* methods and references to *Revision*
Implement the ViewRevisionResource with accompanying test

All tests have been updated to conform to the new old_value/new_value
keys being added to fields in Revision.changes by Avocado now.
Remove stub enpoints for retrieving an object as it was at a revision
Move Revision endpoints to base and extend in object resource creation

Previously the revision endpoints were only fully defined for the View
object. The endpoints were significantly abstract that they could be
moved to base under more general names. Now, the object resource files
need only create url patters and create resources for the different
Revision endpoints, supplying the necessary parameters to the Revision
resource in the constructor.