Remove force geometry flags

With the client-side decoration changes, kwin will properly determine
whether the window needs to be configured even if the frame geometry has
not changed.

This change slightly changes the semantics of the setFrameGeometry()
method. Prior to this, it was possible to force a geometry, i.e. block
other geometry updates, however such a behavior is counter-intuitive and
it exponentially increases the complexity of code.

As far as I know, the force flag was needed to propagate geometry
changes if the frame geometry doesn't change, but the client geometry
does. With the client-side decoration changes, the force flag is not
needed, as kwin now takes into account the client geometry and the frame
geometry when determining whether to send a configure event.