Prevent frontend from starting game w/ >48 hogs
This is because the engine does not support >48 hogs (another bug), but at least this commit a common crash with useless/confusing error message.
07f3bf8d98a3
Hedgewars.png had a resolution more than twice as high as required; also fixed some (mostly obsolete) code that also contained a typo that would cause a warning/note in clang