VDI-1393 Avoid move window outside desktop

This fixes a bug that happened when moving a window outside the desktop.
Now it's not allowed to move the window more than the space with a
margin.
VDI-1393 Don't unbind move event when outside bounds

When moving a window outside the limits of the space the move event used
to be unbinded.
This behaviour is now fixed and you can continue moving until mouseup.
v0.1.16