Support for UUID data type in postgres driver

[saberraz]

Column type UUID in PostgreSQL is not currently recognized by geodiff.

• UUIDs in postgresql are 128-bit identifiers - https://www.postgresql.org/docs/9.1/datatype-uuid.html
• postgres functions to create standard uuids - https://www.postgresql.org/docs/9.1/uuid-ossp.html

On SQLite/GPKG side, there's no special UUID column type, so UUIDs would be treated as text, and if the column type name would be e.g. "uuid" then geodiff would try to convert those to postgresql's uuid column.