431030: Keyboard triggered context menus on ImageField and Button
appears at mouse position instead of field position

Change-Id: I92a3469637a2a417b76bd745b2dc8afb1c2cb3b3
Task-Url: https://bugs.eclipse.org/bugs/show_bug.cgi?id=431030
(cherry picked from commit a54639a38009cb82d64fde269f7b866d6796d83b)
443421: MessageBox shows with big delay

Task-Url: https://bugs.eclipse.org/bugs/show_bug.cgi?id=443421
(cherry picked from commit 0142945e2fd5dcee9207173ecabddf18a3b4b979)

Conflicts:
	org.eclipse.scout.rt.client/src/org/eclipse/scout/rt/client/ui/form/fields/AbstractValueField.java