Fixed issue with double deletion of races and items

Reviewed-by: bjorn.
Added SpriteListModel::setSprites

It does what both NPC and Monster were doing in their constructors,
and it can do it more efficienty (no need for begin/endInsertRows for
each sprite).
Handle waiting for the databases to be loaded

Now Character, Monster and NPC classes will wait with initializing their
sprites until the respective databases have been loaded.
Avoid crashing when receiving an invalid hair style

The reason that I'm getting an invalid hair style is probably protocol
incompatibilities with the lpc2012 branch, but it could happen for
other reasons and it should not crash.