Handle autogrouped clients

This fixes issue #16.
Fix null-pointer dereference in util.compareRect

This broke tabs
Fix wrong comparison in _onClientTabGroupChanged

The Rects need to match (i.e. compareRect returns true) for the client
to be considered part of the tabgroup
Simplify maximized handling
Respect min/maxSize
Prevent tiles from being moved/resized in their own first move/resize step

Set _resize or _move early so we can bail earlier in onClientGeometryChanged
Merge branch '16'