Annotation of sea ice cover min and max depth columns

[kaiiam]

I should make a PATO issue about the annotation of the Depth, top/min and Depth, bottom/max columns from the ice_algal_chlorophyll dataset, which are about the min and max height of sea ice coverage. The PATO term: minimal almost makes sense to use, however that would involve a quality inhering in a quality. I should put this to the PATO community to see how they think this should be handled.

Also mention there is no class: maximal to mirror minimal