[libcontacts] Do not overwrite HasValidOnlineAccount flag

The HasValidOnlineAccount flag is not present in the data received from
the backend, and must be preserved when that is updated.
[libcontacts] Handle dispersed initial query results correctly

When the initial contact set is delivered in multiple events, ensure
that all results are processed.
[libcontacts] Report unknown addresses immediately

When we are asked to resolve an address that was previously resolved
as unknown, report unknown immediately without querying the backend
again.
Merge pull request #65 from matthewvogt/fix-after-merge

Fix issue with populating contact name groups when ContactBrowser invoked