added filament_diameter config setting to Extruder to make volumetric extrusion easier to enable
if filament_diameter is not set or is 0 (or less) then the steps_per_millimeter will be left unaltered
removed unnecessary members from Extruder
added M200 command to set volumetric/linear extrusion mode
Merge pull request #414 from logxen/volumetric

Volumetric extrusion
extended volumetric settings into M92 and M500/M503
Add filament diameter to panel settings
M503 should return steps/mm setting
set the minimum filament diameter to 0.01mm to prevent potential rounding issues
save some ram by not making public data returns static data
Combine some bools to bits
Merge pull request #415 from wolfmanjm/optimize/public-data

save some ram by not making public data returns static data
move big static data structures to USB and NET ram
Merge pull request #416 from wolfmanjm/optimize/bss

move big static data structures to USB and NET ram
clear AHB0 and AHB1 data sections
Merge pull request #417 from wolfmanjm/upstreamedge

clear AHB0 and AHB1 data sections
remove webif as it never worked and has been abandoned
Merge branch 'edge' of github.com:Smoothieware/Smoothieware into edge
Fix extruder SOLO moves when in volumetric mode, so they remain mm and mm/min
Merge remote-tracking branch 'upstream/edge' into upstreamedge
Merge pull request #418 from wolfmanjm/upstreamedge

Fix extruder SOLO moves when in volumetric mode, so they remain mm and m...
Merge remote-tracking branch 'upstream/edge' into upstreamedge
Add zprobe check before move code.