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