#9 alternative db backends

[IOhannes m zmölnig]

it would be great if there were several database backends to be chosen from.

the current jdbm is fine for standalone solutions and for the DVD, but as soon as multiple users want to access the same database, this is hell: there is no locking, so each user works on a local copy of the database; now way is provided to merge these databases (ok, there is a hack(!))

this would be far simpler, if we could connect to a db-server (e.g. postgreSQL or MySQL): atomic transactions and concurrent working on the same dataset!