A compiled ".mrb" script can be specified in the Binding config
subgroup with key 'mrbFile='.
If a 'customScript' is specified it still takes priority however.
time_op now takes 2 optional arguments:
iterations: block will be run this many times and the average
time it took will be printed
opName: tag that is printed before the measured time
Also returns the measured time as float.
I also removed the 'MKXP' module because it was clashing with
the likewise named global const.