set_mob_effect

Simple copy/paste from set_peffect
#2244 ptexp and set_ptexp do not have the correct getter/setter relationship

Because of ... weird bukkit behavior. Code is from Essentials plugin
https://raw.github.com/essentials/Essentials/master/Essentials/src/net/e
ss3/craftbukkit/SetExpFix.java and all credits goes to ementalo,
snowleo and khobbits.
Mostly finished the extension system. Events are confirmed working, functions are untested, but in theory should work.
Merge branch 'master' of github.com:sk89q/commandhelper.git
Fixed player_chat format parameter.
Likely fixed issues with player_chat causing duplicate messages sometimes.
Merge pull request #71 from MariuszT/master

#2244 and set_mob_effect
Merge pull request #72 from jb-aero/pullable

suddenly, ItemMeta
Don't log the error message, as it apparently crashes the server?
Merge branch 'master' of github.com:sk89q/commandhelper.git
fixed test failure and added get_itemmeta and set_itemmeta