Enhancement to M200 (Filament-independent GCode)

The M200 command already allows the setting of the filament diameter in firmware.
With this patch, it can also override bed and extrusion temperatures and extrusion multiplier.
New syntax: M200 T<extruder> D<millimeters> S<extrusion_temp> B<bed_temp> F<flow_multiplier>

When a heating command with temperature >0 is received, the firmware overrides the temperature indication with the one defined in M200.
Temperature = 0 disable the heater as expected