Prevent a StackOverflowError from bubbling all the way up.

This prevents arrays that have circular references that are toString'd from
causing the program to exit with a StackOverflowError.
Merge branch 'master' of github.com:sk89q/commandhelper.git
Added the ability to even have recursive array references.

That wasn't even possible before, as it turns out. Additionally,
we also want to make it so that recursive array references
are possible to toString, which requires reference tracking,
unfortunately.
Added run_cmd(), which is a hybrid call_alias/run type command.
Closures can now return(). If a closure returns inside an execute, then execute will return that value.
Added get_player_from_entity_id.

Also fixed unit tests.
Updated third party dependencies.
Added a message to the debug mode exception handling to show why exceptions are being printed if debug mode is on.
Suppress VerifyError in ClassDiscovery. Hopefully it's not our class that caused the error.
Merge pull request #129 from jb-aero/master

Entity expansions, may fix 2678
Updated to Bukkit 1.6.
Fixed bug 2725.
Merge branch 'master' of github.com:sk89q/commandhelper.git
Fixed a few fringe case bugs with closures and added brace syntax to closures.
Update remaining health functions, potion ids and inventory_click to 1.6