Remove region add duplicate event

fixes #1839
Typo in changelog

and --> on
Updates API README
Fix spelling
Update region-manager.jsdoc
Fix typo
Adds helper methods to AppRouter.
region._ensureViewIsIntact

Having the region check for view.isDestroyed does two things:

1. It allows you to handle the error of a region.show without the region killing the currentView and breaking without recourse.

2. appending isDestroyed to a Backbone.View on region empty adds the same safety for not re-showing a removed backbone view.

The extra return this; was removed to prevent jslint error for too many statements, and seemed unnecessary
Improves Application triggerMethod arguments.
Update param types for addRegion method
Removes unnecessary emptyRegions call in LayoutView.
Updates file names; remove unnecessary files.
Update region-manager.jsdoc
Update param types for addRegion method