Undo in Inputfield is not bound correctly

[CamilleLetavernier]

Original issue: eclipsesource/ecore-glsp#88

During renaming pressing ctrl + z for undoing, the input is not undone, but the class name appears under the input. A second undo removes the class, but the input stays

Instead undo should be bound to the input field, as long as it is selected and not to the whole diagram editor.