Voltage and slow adc naming (#772)

* voltages in python 

* added voltage values in cmd line, added voltagelist in detector class

* voltage values in python

* slow adc list

python/slsdet/__init__.py

@@ -4,6 +4,8 @@
 from .eiger import Eiger
 from .ctb import Ctb
 from .dacs import DetectorDacs, Dac
+from .voltages import DetectorVoltages, Voltage
+from .slowadcs import DetectorSlowAdcs, SlowAdc
 from .detector import Detector
 from .jungfrau import Jungfrau
 from .mythen3 import Mythen3