Window Events on whole tree

[FloVanGH]

Context

At the moment window events stops after occurring on the window. Therefore is not possible to handle window events by other widgets.

Problem description & Solution

Window events should not stop (handled) on window.

[hquil]

Hey, I think this issue might be related, since i only downloaded OrbTK yesterday. Having multiple windows open produces some strange behaviours: (examples from git, windows release)