Bug 552385 - EMFDeleteServiceImpl contradicts model's item providers

Add an extension protocol for conditional deletion support.
Use it in the UI for delete action enablement.

Change-Id: I83cf91ec2792ad5bf1fd658e37dc88b1dc2d3ec1
Signed-off-by: Christian W. Damus <give.a.damus@gmail.com>
12 files changed