Since 3.15.2, the cells keyword of cf.aggregate allows fields to be aggregated sperately according to the characteristics of their dimension coordinates - namely cell spacing and cell size.

It would be useful to automatically record these characteristics on the aggregated fields, so that it is easy to see afterwards which conditions were passed.

Since the characteristics apply to dimension coordinate constructs only, they should be recorded on those constructs.

I propose four new DimensionCoordinate methods of [del|get|has|set]_cell_characterstics to allow the cell characteristics to be stored and subsequently accessed.