Update Geospatial Metadata/POD Crosswalks (CSDGM, ISO 19115, and ISO 19115-1)

[LyndaW]

Review and finalize crosswalks between POD data.json and CSDGM and ISO 19115 geospatial Metadata Standards.
Include development of POD/ISO 19115-1 crosswalk.

Resources:

• Published crosswalks: https://project-open-data.cio.gov/v1.1/metadata-resources/#crosswalks-for-geospatial-metadata
• CSDGM Crosswalk Working Doc: https://docs.google.com/spreadsheets/d/13HBHMqVqitBIu5AIs6fIzUuT3yebNhn3s2UF9iVyYa4/edit#gid=0
• ISO 19115 Crosswalk Working Doc: https://docs.google.com/spreadsheets/d/13K94gLYTnf0uzeBeAU6C70BCd2HVUtdM2VaK1tbhHRU/edit#gid=1807133374 (access by gmail only, request access from [email protected])

Reference Issue: #555