fixed gear motor spindle being detached from body by 1 unit
readded 2 extra holes to idlers, to make it require 4 bolts (2 bolt solution impedes filament)
changed width of carriage to accodomate correct fitting of 2nd idler
extra support material just after motor spindle plus minor tweaks to shapes to make them fit
added 'display' module to show final extruder assembled with geared motor