ADD: added the crc8legic to Lua. call it with core.crc8legic

      also a helper function to take a hexstring and calc the crc on it, was added inside utils.lua

   Call it inside a lua-script like this:

        local utils = require('utils')
        local data = '01020304'
	local crc = utils.Crc8Legic(data)
	print (uid,  ('%02x'):format(crc))