DINAA Specific - Add NRHP filter to common standards

[rcdemuth]

An NRHP filter would be useful for the DINAA data, it looks like most of the states included their NRHP status data in their data transfers, it would be helpful (and potentially very simple) to create a common filter to 'translate' this across state lines.

[ekansa]

Good idea. We should start a common controlled vocabulary for NRHP status. Can you propose a list of common terms + definitions (share with group on Google Docs?)