Bug 552715 - [Validation] Validation providers should be given the view model context

Add optional API for ValidationProvider implementors to get access to
the view model context.  Ensure in the ValidationServiceImpl that all
providers added to it, including registrations on the extension point,
get that context passed through the core validation service to which
they are attached.

Change-Id: I7ed27314a93a4195eb243dffc0780a4c2b70a166
Signed-off-by: Christian W. Damus <give.a.damus@gmail.com>
5 files changed