Add height/width measurement unit to cvs export

[timelf]

How can we include the measurement unit for the height / width field in the cvs export: In the template I'm working on, I've added it as another field immediately after the heigh and width fields.

[rhigman]

Added under #279: CSV export now has separate fields for width (mm), width (cm), width (in), height (mm), height (cm) and height (in). Note that CSV exports can be publicly requested by anyone, and units selection is only available to logged-in users, so adding a separate "units" column (as in the screenshot) would not have been appropriate.