Added basic screen to add incoming webhooks

webapp/components/form_error.jsx

@@ -0,0 +1,50 @@
+// Copyright (c) 2016 Mattermost, Inc. All Rights Reserved.
+// See License.txt for license information.
+
+import React from 'react';
+
+export default class FormError extends React.Component {
+    static get propTypes() {
+        // accepts either a single error or an array of errors
+        return {
+            error: React.PropTypes.node,
+            errors: React.PropTypes.arrayOf(React.PropTypes.node)
+        };
+    }
+
+    static get defaultProps() {
+        return {
+            error: null,
+            errors: []
+        };
+    }
+
+    render() {
+        if (!this.props.error && this.props.errors.length === 0) {
+            return null;
+        }
+
+        // look for the first truthy error to display
+        let message = this.props.error;
+
+        if (!message) {
+            for (const error of this.props.errors) {
+                if (error) {
+                    message = error;
+                }
+            }
+        }
+
+        if (!message) {
+            return null;
+        }
+
+        return (
+            <div className='form-group has-error'>
+                <label className='control-label'>
+                    {message}
+                </label>
+            </div>
+        );
+    }
+}