Extract repetitive CSS inline styles

Inline styles slow down rendering proportionally to containers number

src/css/less/grafana.less

@@ -6,6 +6,12 @@
 @import "search.less";
 @import "panel.less";
 
+.row-control-inner {
+  padding:0px;
+  margin:0px;
+  position:relative;
+}
+
 .hide-controls {
   padding: 0;
   .row-control-inner {