use new icon set

adopt UI to use new icon set

website/agenda/planung/js/history.js

@@ -133,11 +133,16 @@ function addBackButton(){
     // add back button if history exists
     var history=getHistory();
     //console.log(history.length);
-    if (history.length>1)  $('#calcms_admin_menu').first().prepend(
-        '<div><a id="backButton" href="#" onclick="getBack();">'
-        +loc['button_back']
-        +'</a></div>'
-    );
+    if (history.length>1){
+        $('#calcms_admin_menu').first().prepend(
+            '<div><a id="backButton" href="#" onclick="getBack();">'
+            +'<i class="fas fa-caret-square-left fa-1g"></i>'
+            +'&nbsp'
+            +loc['button_back']
+            +'</a></div>'
+        );
+    }
+    setupMenuHeight();
     //showHistory();
 }