Units fixes web

[will-moore]

A couple of fixes found so far for units changes in develop:

Fixes display of ROIs in web image viewer http://trac.openmicroscopy.org.uk/ome/ticket/12640

Also display of channel labels in images where label is derived from wavelength. To test this, find an image with channel emission wavelength and re-import or remove any existing channel name via editing channels.

[joshmoore]

>       set_if('strokeWidth', shape.getStrokeWidth().getValue())
E       AttributeError: 'NoneType' object has no attribute 'getValue'
omeroweb/webgateway/marshal.py:276: AttributeError

I also wonder if we should all use the same #FIXME test so that we can find all these assumptions during the next step.

[gusferguson]

Tested using http://trout.openmicroscopy.org/merge/webclient/userdata/?experimenter=5 user-4 read-write-1 and read-only-1.

Image cited in ticket 12640 and other images behave as expected. No issues with ROI viewing or channel names.
Good to merge.

[joshmoore]

--no-rebase