Replace mesecon:<some_function> with mesecon.<some_function> for greater
flexibility and because it was never inteded to be OOP in the first
place.

mesecon.receptor_on and mesecon.receptor_off are provided by wrappers
(mesecon:receptor_on/off) for compatibility, but will be removed. Mod
programmers that use mesecons: Please update!

Also, fix microcontroller polluting the global namespace and remove some
deprecated stuff.