Refactor protocol buffer to split models into different packages

Change-Id: I26152ba227ebe9afd871c6e501ccca17c49e1e4e
diff --git a/incubator/rpc-grpc/src/main/proto/LinkService.proto b/incubator/rpc-grpc/src/main/proto/LinkService.proto
index ee32453..e211e11 100644
--- a/incubator/rpc-grpc/src/main/proto/LinkService.proto
+++ b/incubator/rpc-grpc/src/main/proto/LinkService.proto
@@ -1,7 +1,8 @@
 syntax = "proto3";
 option java_package = "org.onosproject.grpc.net.link";
 
-import "models/Link.proto";
+import "net/link/LinkDescriptionProto.proto";
+import "net/ConnectPointProto.proto";
 
 package Link;
 
@@ -11,15 +12,15 @@
 message LinkDetectedMsg {
   // ProviderId scheme only
   string provider_id = 1;
-  LinkDescription link_description = 2;
+  net.link.LinkDescriptionProto link_description = 2;
 }
 
 message LinkVanishedMsg {
   // ProviderId scheme only
   string provider_id = 1;
   oneof subject {
-    LinkDescription link_description = 2;
-    ConnectPoint connect_point = 3;
+    net.link.LinkDescriptionProto link_description = 2;
+    net.ConnectPointProto connect_point = 3;
     string device_id = 4;
   }
 }