Add importing of ini config from verbose gcode

It's works as well as I think it could do with the current output format of verbose gcode. It's not catastrophically slow, I tested on up to a 35MB file. It will die with a useful message if the gcode file doesn't have a config, not useful to GUI users, much like invalid ini files.

I think it would be a wise to next add ini configs to the end of all gcode with a nice start and end header.
Well, that didn't take long. Perhaps better to search for the "exported by slicer version" string and choose a min level.