motor valve using trinamic motor

This valve needs 8 turns to open. As the encoder forgets
the number if turns on power cycle, a home switch is
mounte, which engages during the last turn when closing.
The final close position is determined by closing the valve
with a defined motor current/torque.

+ fix an issue in StateMachine.start: the first cycle
  must be called after the new state is assigned

Change-Id: I34cd05d10d97b043f9e3126310943b74ee727382
Reviewed-on: https://forge.frm2.tum.de/review/c/sine2020/secop/playground/+/28030
Tested-by: Jenkins Automated Tests <pedersen+jenkins@frm2.tum.de>
Reviewed-by: Enrico Faulhaber <enrico.faulhaber@frm2.tum.de>
Reviewed-by: Markus Zolliker <markus.zolliker@psi.ch>

test/test_statemachine.py

@@ -78,7 +78,6 @@ def test_fun():
     s.cycle()  # do nothing
     assert s.step == 0
     s.start(rise, level=0, direction=0)
-    s.cycle()
     for i in range(1, 4):
         assert s.status == 'rise'
         assert s.step == i
@@ -100,7 +99,6 @@ def test_fun():
 def test_max_chain():
     s = StateMachine(step=0, status='', threaded=False, logger=LoggerStub())
     s.start(fall, level=999+1, direction=0)
-    s.cycle()
     assert isinstance(s.last_error, RuntimeError)
     assert s.state is None