refactor current control to save memory
M500 now saves all currents for all configured channels
Merge pull request #459 from wolfmanjm/refactor/digipot

refactor current control to save memory
cleanup include files
Merge pull request #460 from wolfmanjm/upstreamedge

cleanup include files
fix current control bug introduced by refactor
Merge pull request #462 from wolfmanjm/upstreamedge

fix current control bug introduced by refactor
update firmware.bin and checksum