Also reset E using G92 on BFB and Makerbot flavours
The original commit says that it's not supported well. However, the RepRapWiki says it's supported nowadays. Maybe the earlier firmware had some trouble there.
I'm still not resetting the E value after E10,000 though, just to be sure. It's only resetting the E value in an extruder switch, which was causing a crash because it assumed (and asserted) that the E value was 0 after an extruder switch.
Don't insert temperature command if there is a zero-length move in an extruder plan
If there are only zero-length moves in an extruder plan, it's not properly detected that the extruder plan is empty. To properly detect that, you'd need to compute the total time estimate and see if that is zero. This takes computing power though, but luckily we already have the time estimate here just in time to do something about it.
