connect to db on request not on startup

[schdief]

We have a problem that when the app starts and the db is not available, it will never work. Also when the app is running and connected to the db and the db fails, then the app will never reconnect (probably the reason for the downtime on September 11th). We should move the connection to request level in such a way, that for every request it is checked whether the db is connected and if not, a new connection will be set up. If this fails, we'll retry it 3 times with 10s timeouts and then fail the request.