Adding edit of incoming webhook (#5272)

Adding edit of outgoing webhook
Fixing spelling of error
Fixing style
Changing from PUT to POST for updates
Fixing test failures due to merge

webapp/utils/constants.jsx

@@ -105,6 +105,7 @@ export const ActionTypes = keyMirror({
 
     RECEIVED_INCOMING_WEBHOOKS: null,
     RECEIVED_INCOMING_WEBHOOK: null,
+    UPDATED_INCOMING_WEBHOOK: null,
     REMOVED_INCOMING_WEBHOOK: null,
     RECEIVED_OUTGOING_WEBHOOKS: null,
     RECEIVED_OUTGOING_WEBHOOK: null,