fresh() for clearing out the current VM state

[trentgill]

currently when you want to script with First running, you have to upload a stop.lua file, or at least turn off all the standard features.

this function should:

• set inputs mode to 'none'
• set outputs volts & slew to 0
• stop all metros

[pq]

related: https://github.com/monome/norns/pull/894 where we are doing this on the norns side.