more & better error messages

[knorke]

When a 3d model file is faulty Spring should say so in infolog instead of just crashing without any meaningfull message.
Same with units, effects, weapons etc.

[smoth]

http://springrts.com/mantis

[knorke]

ok, thought thats just for error reports not wanted features.
anyway:
http://springrts.com/mantis/view.php?id=2228

[FLOZi]

http://springrts.com/mantis/view.php?id=2178

[Tobi]

ok, thought thats just for error reports not wanted features.
anyway:
http://springrts.com/mantis/view.php?id=2228

A reproducable crash = a bug, regardless of the state of the input (good/bad) (and unless stated otherwise)

(not necessarily a bug in Spring though!)