Handle units on workingDistance
Fixing long lines in MetadataFilterForm
Removing unused imports from webclient/forms.py
Handle units on Filter transmittanceRange cutIn, cutOut etc
Fixing long lines in MetadataDetectorForm
Handle units on DetectorSettings Voltage
Fix long lines in MetadataLightSourceForm
lightSource variable to avoid repetition
Handle units on LightSource wavelength
Fix long lines in MetadataChannelForm
logicalCh variable to avoid repetition
Handle units on Channel Pin Hole Size
Use detectorSettings variable to avoid repetition
Handle units on DetectorSettings ReadOutRate
Fixing long lines in ImagingEnvironment
Handle units on ImagingEnvironment temperature
Handle units on ImagingEnvironment AirPressure
Initial conversion code via ctors

As described on openmicroscopy/ome-documenation#1041,
this enables converting from most enums of one unit
to another.
Use target unit during conversion
Add a simple units tests for conversions