Pulled latest master from kliment/printun and changed extrusion length
to a hidden setting. It is now saved upon change as
settings.last_extrusion and can be set as such. Also added default
extrusion length that may be used as a fall back for deploying printrun
with a different default extrusion length without having to change that
everywhere in the code.

Removing legacy uploads directory (gcode files are stored in ram now for better performance on the raspberry pi).