Migrate to PostgresQL database backend

[bark10]

Our sqlite world has exceeded 4 gb (currently at 5.5) so we need a new database backend to handle the increased size. PostgreSQL seems like the best alternative.

Advantages

• Greater use of memory to improve performance
• Automatic re-indexing using the auto vacuum feature
• Backups while minetest users are playing
• Continuous backups, using automatic transaction log archiving
• Ability use separate application and database server, for increased performance
• Redundancy, load balancing, and failover, via PostgreSQL features
• Use of triggers and additional columns or tables

[bark10]

On its way.

[bark10]

Issue closed. I did not go with the PostgreSQL database backend as it required too much time to get working. The world has successfully been migrated to LevelDB.