A bunch of new stuff

LuaScriptInterface::set*Metatable should not be confusing to use (index)
Added 2 new metatables (Guild, Group)
Added 3 functions to the Position metatable (isSightClear,
sendMagicEffect, sendDistanceEffect)
Removed unneccesary garbage collection functions and made it work a
little better.
Added 10 functions to the Player metatable
(getMagicLevel, getManaSpent, addManaSpent, getSkillLevel,
getSkillPercent, getSkillTries, addSkillTries, getItemCount,
getItemById, getSlotItem)