Improve the LuaController

Changes:
  * Stops code after a certain number of instructions.
  * Allows functions, due to instruction counting.
  * Allows loops and goto with non-JIT Lua (LuaJIT doesn't count looping as an instruction, allowing infinite loops), due to instruction counting.
  * Removes string matching functions as they can be slow.
  * Adds some safe functions.
  * Limits the amount of printing that can be done (to prevent console flooding).
  * Code cleanup.
  * More...
Merge branch 'improve-luacontroller' of https://github.com/ShadowNinja/minetest-mod-mesecons into ShadowNinja-improve-luacontroller

Conflicts:
	mesecons/legacy.lua
	mesecons_luacontroller/init.lua
	mesecons_microcontroller/init.lua
Fix burnt luacontroller, nodebox + crash
Merge branch 'improve-luacontroller'

However, without the print_count limiting functionality

Conflicts:
	mesecons_luacontroller/init.lua