Send solicit message when new neighbour is discovered

router/proto/router.proto

@@ -7,6 +7,7 @@ service Router {
 	rpc Lookup(LookupRequest) returns (LookupResponse) {};
         rpc Watch(WatchRequest) returns (stream Event) {};
         rpc Advertise(Request) returns (stream Advert) {};
+        rpc Solicit(Request) returns (Response) {};
         rpc Process(Advert) returns (ProcessResponse) {};
 	rpc Status(Request) returns (StatusResponse) {};
 }
@@ -22,6 +23,9 @@ service Table {
 // Empty request
 message Request {}
 
+// Empty response
+message Response {}
+
 // ListResponse is returned by List
 message ListResponse {
 	repeated Route routes = 1;