Add mcp4728 support

for current controll with dac
add an optional kill button which can be on the pause button pin or on a different pin
add to config
fix typos
Merge remote-tracking branch 'upstream/edge' into feature/kill-button
minor refactor of gcode dispatch
Merge remote-tracking branch 'remotes/upstream/edge' into edge
added mv command to simpleshell
added rename() to stdio.cpp
added ready() to StreamOutput
add upload command to SimpleShell
Merge pull request #534 from wolfmanjm/add/mv_and_upload_commands

added mv command to simpleshell
added max_temp config option to temperaturecontrol
fix typo
Merge pull request #535 from Smoothieware/max-temp

Confirmed to work
update firmware.bin
Add multiple temps to panel watchscreen if there are more than two enabled, top line cycles through different temps every 5 seconds
Merge pull request #536 from wolfmanjm/feature/more-temps-in-watchscreen

Add multiple temps to panel watchscreen if there are more than two enabl...
add icons for hotends 2 and 3
Merge pull request #537 from wolfmanjm/upstreamedge

add icons for hotends 2 and 3
update firmware.bin
add StepperMotor::get_last_milestone()
Merge pull request #538 from wolfmanjm/upstreamedge

add StepperMotor::get_last_milestone()
add P1.18, P1.20, P1.21, P1.23 as laser PWM pins