Bug 519607 - Add support for Multi edit

* fixes application of multi editing context behavior only if
multi-selection occurs
* add support for add/remove notifications
* enable multi editing on view model editor
* add test case

Change-Id: I1e664caeac2fd56fff0beb80794df994981f95c9
Signed-off-by: Eugen Neufeld <eneufeld@eclipsesource.com>
4 files changed