Release Qt UI Tools library under BSD license

The Qt UI Tools library is built statically by default. We should
therefore release it under a more liberal license than BSD. This follows
the example of the qtmain library, which is also available under BSD.

[ChangeLog][Licensing] The Qt UI Tools library got relicensed to
commercial + BSD.

Change-Id: I0de0f5213305d148dcc64ab02177b92e99e3eb43
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@qt.io>
Reviewed-by: Lars Knoll <lars.knoll@qt.io>