Part way through migrating DigitalContent to Marionette.

End-of-day checkin.
Migrate ContentTypeView to Marionette.

Still need to migrate Item and DigitalContent Views.

Related to Issues #18 and #15, and will help with issue #23.
Fix ViewModel to correctly inherit from Backbone.Model

Very important fix, without it Backbone can't recognise class as
a Model.
Add 'title' parameter to Content List Template
Progress on migrating DigitalContent

Now displays content correctly without error.

Other than that, untested.

See issues #23, #18, and ultimately #15
Remove debug line
Merge pull request #24 from recurse/migrateDigitalContent

Migrate digital content