fix: Enter key does not stage/unstage all selected items

[mgarstenauer]

The Space and Enter keys can be used to stage or unstage the selected items in the working copy. The Space key works correctly, but the Enter key does not.

Cause:

The ListBox in the ChangeCollectionView changes the selection when Enter is pressed before WorkingCopy can stage/unstage the selected items.

Solution:

Same as for Space. The ChangeCollectionView should ignore the Enter key and not forward the KeyDown event to the underlying ListBox.