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
Add support for blocking sub commands
Allow EnderPearls to damage the player who threw them in no-pvp areas
Decrease call to PluginManager in WGBukkit

If WorldGuard is already found we bypass the call to
the PluginManager and use a cached version.
Added MAX_PLAYER and MAX_PLAYER_MESSAGE flags
Allows setting maximum number of players in a region
and sends a message if a region is at capacity.
Fix players being able to plant cocoa beans in protected areas
Add enderpearl flag to prevent players from teleporting to/from regions with enderpearls
Added config setting and flag to block explosions by plugins.
Mob damage setting/flag blocks poison DoT
Fireball flag should block blaze fireball ignition too now
Fixes for tripwire, flower pots, wooden buttons, ender chests, and sneaking
Added config option to block zombies from breaking down doors
Added changelog for 5.7. Incremented version in pom.xml.
Fix enderpearl flag properly
Remove max players flag for now.
There are currently too many unhandled circumstances
which can easily break this flag such as players
entering region in weird ways (teleporting, falling,
logging in) and states changing. It is also horribly
inefficient at the moment.
[maven-release-plugin] prepare release 5.7
[maven-release-plugin] prepare for next development iteration