add more prominent button for switching edit mode

public/app/plugins/datasource/postgres/partials/query.editor.html

@@ -105,6 +105,12 @@
         <select class="gf-form-input gf-size-auto" ng-model="ctrl.target.format" ng-options="f.value as f.text for f in ctrl.formats" ng-change="ctrl.refresh()"></select>
       </div>
     </div>
+    <div class="gf-form">
+      <label class="gf-form-label query-keyword" ng-click="ctrl.toggleEditorMode()">
+        <span ng-show="ctrl.target.rawQuery">Query Builder</span>
+        <span ng-hide="ctrl.target.rawQuery">Edit SQL</span>
+      </label>
+    </div>
     <div class="gf-form">
       <label class="gf-form-label query-keyword" ng-click="ctrl.showHelp = !ctrl.showHelp">
         Show Help