Add representers as a category of extension; these are extra
steps to perform when representing a domain object. This
will be used to support automatic mutation/persistence of
domain objects from a watch, while avoiding bloat within
the mct-representation directive itself. This, in turn,
simplifies the persistence strategy to be employed by
Layout views when editing concludes. WTD-535.
Fix extension definitions related to the refactoring
of GestureProvider out of the mct-representation
directive. Completing work on the initial version
of the representation bundle, WTD-521.
Add spec for the mct-representation; separate out gesture
attachment to improve testability and increase cohesion.
Part of ongoing initial authorship of representation
component, WTD-521.
