databases/postgis30: Geographic objects support for PostgreSQL databases

• Add CONFLICTS_INSTALL for databases/postgis2*
• Add USE=NLS for databases/postgis2*
• New port databases/postgis30
• New default options for postgis: WAGYU, PROTOBUF and JSON
• RASTER is now a separated extension (enabled by default), use "CREATE EXTENSION postgis_raster;" as for topology or sfcgal extensions

Changelog:

https://postgis.net/2019/10/20/postgis-3.0.0/

PR: 241358
Submitted by: Loïc Bartoletti <lbartoletti@tuxfamily.org>