Update dev doc, add info about dbserver
Update dev doc, add info about dbserver


Former-commit-id: b968f668ec91c6c37ae648d0a0e6e652f3fe1cf2 [formerly a9012a66508a3076ad8496f5ec38c5551ec98079]
Former-commit-id: 589fa342b406963493cfb9951eb3783f68422a70
gem/oq-engine,gem/oq-engine,gem/oq-engine,gem/oq-engine,gem/oq-engine