sidebar chacked button

app/less/app.less

@@ -31,6 +31,10 @@ footer {
   line-height: 30px;
 }
 
+.md-group-button-checked {
+  background-color: rgba(0, 0, 0, 0.12);
+}
+
 .md-sidebar {
   height: 100%;
   min-height: 150px;

app/views/sidebar.html

@@ -19,7 +19,7 @@
             </li>
             <li ng-repeat="group in getCurrentGroups()" class="col-xs-12">
                 <md-button class="md-primary md-hue-1 md-group-button col-xs-12"
-                           ng-class="{'md-focused': DataShareBusiness.getCurrentGroup().Id == group.Id}"
+                           ng-class="{'md-group-button-checked': DataShareBusiness.getCurrentGroup().Id == group.Id}"
                            ng-href="{{DataShareBusiness.getGroupUrl(group)}}">
                     {{ group.Name }}
                 </md-button>