rework of serial interface
- only 1 response per cmd, plus maybe later position reports
- consistency in output format, everything is comma separated or bitstream.
- `|` now reports voltage
- limits delimited by `/`
no travel past end of limits
simplify probe failure reports. works with kiosk 0c54269
Merge branch '4axis' into response-simplify
added new command for sequenced-start
honor settings seek rate
fix homing speed, flash-s0 script
merged checksum code
Merge branch 'response-simplify' of https://github.com/keyme/grbl into response-simplify
Added extra print on probing - sometimes we were losing it.
Add support for realtime counter queries.
 - reworked sysflags, because I ran out of bits.
removed all the line number  #defines - we are always going to use them
restored overly aggressive deletion
Don't Alarm on probe fail, only report
rework of serial interface
- only 1 response per cmd, plus maybe later position reports
- consistency in output format, everything is comma separated or bitstream.
- `|` now reports voltage
- limits delimited by `/`
no travel past end of limits
simplify probe failure reports. works with kiosk 0c54269
added new command for sequenced-start
honor settings seek rate
checksumming responses