Currently, incremental syncing (text first, then photos) can only be controlled
by an env variable (SYNCEVOLUTION_PBAP_MODE). It would be better to have an
explicit parameter to SyncPeer() and the syncevolution command line for that,
because changing the env variable of a running syncevo-dbus-server is not
possible.

The command line switch could also be used to enable "ephemeral" syncing where
no meta data gets written. That would bring debugging via the command line one
step closer to syncing via SyncPeer().