CORE-3922 Updated CollaboratorsUtil to fire events on add and remove.

Added CollaboratorsAddedEvent, CollaboratorsRemovedEvent, and associated Handler interfaces.
Updated CollaboratorsDialog to use a standard size no matter where its launched from.
CORE-3922 Added Manage Collabs button to SelectCollaboratorsDialog.

Added a button to the bottom toolbar of the SelectCollaboratorsDialog that opens the Collaborators management dialog.
Added event handlers to the SelectCollaboratorsDialog so that its grid is updated on collaborator added and remove events.
Updated the SelectCollaboratorsDialog grid's empty text with instructions to use the "Manage Collaborators" button.