#173 - Slight refactoring of associating admin form actions to an EntityForm; initial prep for implementing an extension manager pattern
(cherry picked from commit e7008d4fd6bcf4e5b49d7e4b6b60a93a78318761)
Added extension manager for adding controls to the admin form
(cherry picked from commit 26e3f962777b2e03634d435f64ec6f10e03da72b)
#173 Added support to create additional buttons or actions on admin
forms without extending a controller.