Use ng-model when communicating state to/from the
tree in browse mode. This will simplify implementation
of the Locator control, which also uses a tree, but
which should not set navigation state. WTD-593.
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.
Add spec for ContextMenuGesture, which exposes a menu
of applicable actions for objects when it is performed.
One of the built-in gestures supported by the
representation component, WTD-521.