Prevent heating after Stop() is called

[awenelo]

Check IsStopped() before setting temperatures. This is an alternative to #2609 and fixes #2605.

Additions:

• Check IsStopped() before heating, don't heat if true

• If the Gcode M104, M109, M140 or M190 is called and IsStopped() is true, we don't set temperature, and send Hotend/Bed temperature not set because Stop() has been called. Use M999 to reset and try again. over serial.

• Don't show menu items that cause heating if IsStopped() is true

  • Preheat
  • Print from SD
  • Load filament
  • Unload filament
  • Settings > Temperature