Add close button to Slash Commands /help dialog

Signed-off-by: Michael Telatynski <7t3chguy@gmail.com>

src/SlashCommands.js

@@ -837,6 +837,7 @@ export const CommandMap = {
                     }
                     </tbody>
                 </table>,
+                hasCloseX: true,
             });
             return success();
         },

src/components/views/dialogs/InfoDialog.js

@@ -28,12 +28,14 @@ export default React.createClass({
         description: PropTypes.node,
         button: PropTypes.string,
         onFinished: PropTypes.func,
+        hasCloseX: PropTypes.bool,
     },
 
     getDefaultProps: function() {
         return {
             title: '',
             description: '',
+            hasCloseX: false,
         };
     },
 
@@ -48,7 +50,7 @@ export default React.createClass({
             <BaseDialog className="mx_InfoDialog" onFinished={this.props.onFinished}
                 title={this.props.title}
                 contentId='mx_Dialog_content'
-                hasCancel={false}
+                hasCancel={this.props.hasCloseX}
             >
                 <div className="mx_Dialog_content" id="mx_Dialog_content">
                     { this.props.description }