cubicweb-postgis #3036193 Provide a default field mapping for Geometries [validation pending]

CubicWeb expects all base types to have a form field. The cube should at least provide a default one.

prioritynormal
typebug
done in0.1.0
load0.100
load left0.000
closed by#5433627fba4d [views] use StringField to edit geometries (closes #3036193)
patch[views] use StringField to edit geometries (closes #3036193) [applied]