Build on latest Bukkit snapshot. Closes WORLDGUARD-2381

Fixes EntityChangeBlockEvent errors. Note that 1.4.5-R0.3-SNAPSHOT means build 2505+ and that there ARE 0.3 snapshots below 2505. Thus, this should be treated as temporary and changed on the next Bukkit Beta.
Null check for entity explosions without an entity.
Block snowballs in pvp regions again. Reverts 671fd58568
Attempt to fix item frame issues
Merge remote-tracking branch 'sk89q/master'

Conflicts:
	pom.xml