When level is unknown, don't go up but wait for a first setLevel command

[mosseb]

Allow LEVEL_NONE as valid in the StoredState. At initialization, don't go up immediately, but wait for a setLevel command that is 0 or 100 to start moving. Only then, go to the STATE_RESETTING state. When in STATE_RESETTING state, don't accept other setLevel or stop commands until the move is finished, that is we are back in STATE_IDLE with a known level.

[cribskip]

@marvinroger I beg you, please merge this PR :-)