Closes #10

Closes #7

Closes #2

Closes #5

Closes #4

Closes evolution-data-server#12

This is a just-in-case change, which avoids re-using connection which
had been reported as offline (when the backend/store disconnected).

Reported downstream at:
https://bugzilla.redhat.com/show_bug.cgi?id=1567572

Online GAL could return Contact information with empty street
addresses, which had been shown empty in Evolution as well, but
such addresses do not have much meaning, thus skip them.

Reported downstream at:
https://bugzilla.redhat.com/show_bug.cgi?id=1565343