Video player sizes down vertically as well as horizontally

The x button is also not cut off.

The sides of the player still get a bit cut off at some very small resolutions.
But this should work at least until 800x600.
[endlessm/eos-shell#3973]
Restrict the minimum window height to 600x400

Its still basically unusable at this resolutions, but any smaller
than this and things start to look crazy
[endlessm/eos-shell#3973]