Rename preferences for ChangeScreen2 to "New Change Screen"

ChangeScreen2 is an internal name and shouldn't be exposed to the
users. Since the preference for the old change screen is names "Old
Screen" it is consistent to name the preference for the new change
screen "New Screen".

Change-Id: Iaba3e5010fc935efa024bb97dbf388d399d2bfbe
Signed-off-by: Edwin Kempin <edwin.kempin@sap.com>