Length: stage positions
Length: stage labels
WIP: unorganized and not even single-checked.

Fixes so far have not been carefully re-read.
Tests fail with,
loci.common.services.ServiceException: ome.xml.model.enums.EnumerationException: 'referenceFrame' not a supported value of 'class ome.xml.model.enums.UnitsLength'
Correcting typo in reference frame
Merge branch 'mtbc-andrew-units-work' into units-length