It's now possible to regenerate the protobuf files by calling 'go
generate' in rpc/. You will need protoc and protoc-gen-go in PATH.
This is only necessary after changing the protobuf definitions.
UNKNOWN is the new default status for contacts. A contact is in the
UNKNOWN state when we're not sure whether they are available or not, and
is in the OFFLINE state when we believe that we're online but attempts
to connect to that contact have failed.