Save image to clipboard support

Copied image doesn't work after the app is closed.

http://stackoverflow.com/questions/2007103/how-can-i-disable-clear-of-clipboard-on-exit-of-pyqt4-application
Causes insane (~3 seconds for 720p) delays on Windows. Qt being Qt.
Relevant reading:
http://www.qtforum.org/article/38905/app-slow-to-exit-after-qimage-copied-to-clipboard.html