Merge pull request #485 from wolfmanjm/upstreamedge

make dtor virtual
If no heaters presume no extruders and do not create extruder menu or temperature relted panel menu items
don't disdplay tmperatures on panel if no heaters
Merge pull request #486 from wolfmanjm/optimize/optionally-load-extruder-menu

Optimize/optionally load extruder menu
Half hearted attempt at implementing M112 ESTOP