added control sidebar #10 (#87)

- added configurable sidebar #10
- added language switch in sidebar preferences tab #10
- added sidebar tab with kimai beta-info message #10
- use trait for repositories
- improved README

public/css/kimai.css

@@ -39,6 +39,11 @@ li.open .ticktac i.running{
 
 /* ================================ TOOLBAR ================================ */
 
+.control-sidebar select {
+    color: #000;
+}
+/* ================================ TOOLBAR ================================ */
+
 .data_table .box-header>.box-tools {
     top: 3px;
 }