Bug 565296 - Allow to pause/resume ViewModelContexts

Added new methods pause/reactivate which allow to ignore notifications
especially while the context is cached.

Pausing a ViewModelContext ignores incoming notifications.
Reactivation does not rereport the ignored notifications.
If you want to update the ViewModelContext state after it was reactived
you should call `changeDomainModel(EObject)` or trigger an event that
fires a notification.

Change-Id: Iac5ba849c962f1a2d16f455091f39bb4be8fff3e
Signed-off-by: Eugen Neufeld <eneufeld@eclipsesource.com>
9 files changed