Support end_date for the update proposal operation changes in hf25

Support end_date for the update proposal operation changes in hf25 (see hive!165 (merged))

src/auth/serializer/src/operations.js

@@ -127,7 +127,7 @@ const smt_param_allow_downvotes = new Serializer(3, {
   value: bool
 });
 
-var update_proposal_end_date = new Serializer(0, {
+var update_proposal_end_date = new Serializer(1, {
     end_date: time_point_sec
 });
 
@@ -721,7 +721,7 @@ let update_proposal = new Serializer(
     daily_pay: asset,
     subject: string,
     permlink: string,
-    extensions: set(static_variant([update_proposal_end_date]))
+    extensions: set(static_variant([future_extensions, update_proposal_end_date]))
   }
 );