Performance of moving windows around is not great

[curzel-it]

Currently, as much as 40% of the CPU used by the app is consumed by moving windows around.
This is currently done via NSWindow.setFrame(:display:animate:).
Disabling animations has virtually no effect on performance.

One idea could be to make the window larger, and move the image instead of the window.
This way, we can move the window itself only once a second or so.
I expect this to be somewhat easier on the CPU, but it's hard to quantity without a spike.