Do not use globals for in LuaScriptObject

Currently the lua script for a script object is like this:

-- Rotator.lua
Rotator = ScriptObject()
-- ...

This is fine, but it uses global to communicate.
It could be better if we do:

-- Rotator.lua
local Rotator = ScriptObject()
-- ...

return Rotator

and use require system or at least the script return value for getting the Rotator object instead of globals.