#17: added form class & interface, added default implementation for
organization entities, added display of update form

Task-Url: https://github.com/mgatz/sunrise/issues/issue/17
#17: added update function for organization entities

Task-Url: https://github.com/mgatz/sunrise/issues/issue/17
#17: deletion is now supported

Task-Url: https://github.com/mgatz/sunrise/issues/issue/17