refactoring of CBattleInterface::show() and all related code
fixes most of blit order-related bugs in battles (#1200, #1238, #226)

known issues, will fix soon:
- there are still some minor blitting issues during movement
- destruction of walls in siege is out of sync with catapult projectile movement

git-svn-id: http://svn.code.sf.net/p/vcmi/code/trunk/@3452 4dfc6b2a-8b31-0410-aa91-d6c70e3ac834