avoid separate "group by" button

src/main/resource/static/search.html

@@ -12,8 +12,8 @@
     gitlab repository</a> for more information)
 <div ng-controller="SearchController">
     <p/>
-    <button ng-click="group()">group by</button>
-    <select ng-model="field" ng-init="columns[shortMsg].long"
+    group by
+    <select ng-click="group()" ng-model="field" ng-init="columns[shortMsg].long"
             ng-options="columns[key].long for key in colProps | filter : '!id'"></select>
     as overview with clickable content