Thanks to std::bind we don't need that many different slots to setup the
global shortcut connections. Instead we can have one shared
implementation which takes the argument and passes it to the window.
To support std::bind arguments in kwinbindings the initShortcut method
and dependencies are adjusted as well as a new macro is added.
As I don't want to include abstract_client.h in workspace.h a new enum
is created for the quick tiling flags used in Workspace. This caused a
larger refactoring as the change to an enum class also caused quite some
changes.