Add disabled handling to InputWidget
Add disabled handling to InputWidget

Currently InputWidget has a readonly state, but not a disabled state;
this adds the latter for cases where the former are not appropriate.

Change-Id: I0afea069b4e0913a656c8ac713a9cee2a47cfa87

wikimedia/oojs-ui,wikimedia/oojs-ui,wikimedia/oojs-ui,wikimedia/oojs-ui