Register of sampling feature types

[KathiSchleidt]

This stems from the SoilIE Results (p 62):
b. A register of sampling feature types building on the informative O&M common sampling features [ISO 19156:2011, clause 10.4] would be useful; this should be a cross domain vocabulary as features like plots are not unique to soil, e.g. ecology.

Not sure if in scope for SWG, but needs to be triggered somewhere