Rewritten entity-on-fire management ("forever on fire" bugs)

Fixes FS #297 and part of FS #403.
Added sizes to all entities.
Moved all damage-related functions from cPawn to cEntity
API change: renamed cPawn:TeleportTo() to cEntity:TeleportToCoords()

git-svn-id: http://mc-server.googlecode.com/svn/trunk@1635 0a769ca7-a7f5-676a-18bf-c427514a06d6