Method no longer virtual and only implemented in AbstractClient.
The implementaton works in a generic way nowadyas.
Added an autotest for the basic packTo behavior for packing against
a screen border. Packing towards other clients still needs adjustments
in the Placement code.
The signals operate on AbstractClient nowadays, so we can have one
implementation for both Client and ShellClient.
Only X specific connections are only done for Client.
So far only moving through useractions menu is possible and only through
cursor control (mouse events are lost).
A basic first autotest is added to validate the moving of Windows.
