UI improvements: fix for wide screens

Yes, again) Centered "Hide movement" vertically.
http://openxcom.org/forum/index.php/topic,1514.msg14043.html#new

Before:
![screen044](https://f.cloud.github.com/assets/3616568/1111280/ee94db02-19a5-11e3-960d-424758bf224b.png)

After:
![screen045](https://f.cloud.github.com/assets/3616568/1111282/fb73fd30-19a5-11e3-87e0-910823a2d63d.png)