Allowing config flag to turn off javascript controls (#4400)

* Allowing config flag to turn off javascript controls

* lint

* one line, avoiding mutation

* Setting JS fields as readOnly

(cherry picked from commit a373db24f0)

superset/assets/javascripts/explore/stores/controls.jsx

@@ -97,6 +97,11 @@ function jsFunctionControl(label, description, extraDescr = null, height = 100,
         {extraDescr}
       </div>
     ),
+    mapStateToProps: state => ({
+      warning: !state.common.conf.ENABLE_JAVASCRIPT_CONTROLS ?
+        t('This functionality is disabled in your environment for security reasons.') : null,
+      readOnly: !state.common.conf.ENABLE_JAVASCRIPT_CONTROLS,
+    }),
   };
 }