Deferring toolbar controller event handler registration

(bug 54098)
In order to improve general JavaScript initialization performance, only the event handlers
that are needed to create a toolbar are defined within the toolbar definition now. All
additional event handlers are registered dynamically as soon as they are required.

Change-Id: Idbe72fb8a1889d992ece9806317e21bc77e6270a
(cherry picked from commit ff9d225d1d9fc24ef9400c010f65d58df72fae71)