Weapons panel improvements
I've taken into account sev's feedback at !106 (merged) and after lots of tests I came up with something good, I think.
To sum it up the changes:
- weapons are now sorted either vertically (more rows) or horizontally (more columns) (not just vertically as before)
- all weapons layout: more symmetrical distribution, icons are now as big as possible
- only owned layout: prefer stretched layouts (like in sev's branch) but avoid too much stretched layouts where item aspect ratio gets altered