set focus on text field when opening panel/query editor (#8879)

* (prometheus) set focus to top expression when opening editor

* (text panel) set focus to top expression when opening editor

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

 <query-editor-row query-ctrl="ctrl" can-collapse="true" has-text-edit-mode="true">
 	<div class="gf-form-inline">
 		<div class="gf-form gf-form--grow">
-			<textarea rows="3" class="gf-form-input" ng-model="ctrl.target.expr" spellcheck="false" placeholder="query expression" data-min-length=0 data-items=100 ng-model-onblur ng-change="ctrl.refreshMetricData()"></textarea>
+			<textarea rows="3" class="gf-form-input" ng-model="ctrl.target.expr" spellcheck="false" placeholder="query expression" data-min-length=0 data-items=100 give-focus="ctrl.target.refId == 'A'" ng-model-onblur ng-change="ctrl.refreshMetricData()"></textarea>
 		</div>
 	</div>
 

public/app/plugins/panel/text/editor.html

@@ -15,5 +15,5 @@
 	(This area uses <a target="_blank" href="http://en.wikipedia.org/wiki/Markdown">Markdown</a>. HTML is not supported)
 </span>
 
-<textarea class="gf-form-input" ng-model="ctrl.panel.content" rows="20" style="width:95%" ng-change="ctrl.render()" ng-model-onblur>
+<textarea class="gf-form-input" ng-model="ctrl.panel.content" rows="20" style="width:95%" give-focus="true" ng-change="ctrl.render()" ng-model-onblur>
 </textarea>