added switching between search engines

- works with different languages
- works with links

refactored selector code:
- changed method names
- changed method parameters (object -> id),
- added method to rename all options of dropdown menu

refactored distance format selector code:
- changed method names
- changed variable names
- changed how to init/select element/change language of dropdown menu

refactored maintenance notification overrides:
- changed names of default variables

WebContent/main.html

@@ -70,6 +70,7 @@ or see http://www.gnu.org/licenses/agpl.txt.
 <script src="routing/OSRM.RoutingDescription.js" type="text/javascript"></script>
 <script src="routing/OSRM.RoutingGeometry.js" type="text/javascript"></script>
 <script src="gui/OSRM.RoutingGUI.js" type="text/javascript"></script>
+<script src="gui/OSRM.RoutingEngineGUI.js" type="text/javascript"></script>
 <script src="routing/OSRM.RoutingNoNames.js" type="text/javascript"></script>
 <script src="base/OSRM.Via.js" type="text/javascript"></script>
 <script src="base/OSRM.Geocoder.js" type="text/javascript"></script>
@@ -207,8 +208,7 @@ or see http://www.gnu.org/licenses/agpl.txt.
     <div class="full">
     <div class="row">
     <div class="left"><a class="button" id="gui-reset">Reset</a></div>
-	<!-- <div class="center"><select id="gui-engine-toggle" class="engine-select"></select></div> -->
-	<div class="center"><a class="button-inactive" id="gui-zoom">Reset</a></div>
+	<div class="center"><select id="gui-engine-toggle" class="engine-select"></select></div>
 	<div class="right"><a class="button" id="gui-reverse">Reverse</a></div>
     </div>
     </div>