Detect DB connection on startup

[heikki]

Time and again people write to the mailing list with a "it does not work" type of problem, that often is caused by a failure to connect to GeoNetwork's database.

If we add a check for this on system startup and if detected there's no connection, display a page saying "there is no connection to the database", I think many problem situations would be cleared up more easily, whether the connection to the DB actually is the problem or not (with this they could rule it in, or out, immediately).

[simonp]

 http://trac.osgeo.org/geonetwork/wiki/StartupErrorsDatabaseConnections