Use SyncJournalDb in csync

Use SyncJournalDb in csync

This gets rid of the csync_statedb sqlite layer and use
the same code and same connection as the rest of the SyncEngine.

Missing functions are added to SyncJournalDb and change a few minor
things (like changing SyncJournalFileRecord::_modtime to be an int64
instead of a QDateTime, like it was in csync).