grpc - add rpc to get local non-core interfaces

daemon/proto/core/api/grpc/core.proto

@@ -115,6 +115,10 @@ service CoreApi {
     }
     rpc OpenXml (OpenXmlRequest) returns (OpenXmlResponse) {
     }
+
+    // utilities
+    rpc GetInterfaces (GetInterfacesRequest) returns (GetInterfacesResponse) {
+    }
 }
 
 // rpc request/response messages
@@ -622,6 +626,13 @@ message OpenXmlResponse {
     int32 session_id = 2;
 }
 
+message GetInterfacesRequest {
+}
+
+message GetInterfacesResponse {
+    repeated string interfaces = 1;
+}
+
 // data structures for messages below
 message MessageType {
     enum Enum {