Add support for WMTS capabilites

https://github.com/klokantech/tileserver-gl/issues/274

Clean up wmts template with correct syntax

Update endpoint URL and change content type

After a good nights sleep I considered the structure of the endpoint link for WMTS, at the same time I cleaned up the code and added the correct content type for the response.

src/server.js

@@ -269,6 +269,7 @@ function start(opts) {
           data['key_query_part'] =
               req.query.key ? 'key=' + req.query.key + '&' : '';
           data['key_query'] = req.query.key ? '?key=' + req.query.key : '';
+          if(template === 'wmts')res.set('Content-Type', 'text/xml');
           return res.status(200).send(compiled(data));
         });
         resolve();
@@ -325,11 +326,6 @@ function start(opts) {
               Math.floor(centerPx[1] / 256) + '.' + data_.format;
         }
 
-        var query = req.query.key ? ('?key=' + req.query.key) : '';
-        data_.wmts_link = 'http://wmts.maptiler.com/' +
-          base64url('http://' + req.headers.host +
-            '/data/' + id + '.json' + query) + '/wmts';
-
         var tiles = utils.getTileUrls(
             req, data_.tiles, 'data/' + id, data_.format, {
               'pbf': options.pbfAlias
@@ -374,6 +370,20 @@ function start(opts) {
     return res.redirect(301, '/styles/' + req.params.id + '/');
   });
   */
+  serveTemplate('/styles/:id/wmts.xml', 'wmts', function(req) {
+    var id = req.params.id;
+    var wmts = clone((config.styles || {})[id]);
+    if (!wmts) {
+      return null;
+    }
+    if(wmts.hasOwnProperty("serve_rendered")&!wmts.serve_rendered){
+    return null;
+    }
+    wmts.id = id;
+    wmts.name = (serving.styles[id] || serving.rendered[id]).name;
+    wmts.baseUrl = (req.get('X-Forwarded-Protocol')?req.get('X-Forwarded-Protocol'):req.protocol) + '://' + req.get('host');
+    return wmts;
+  });
 
   serveTemplate('/data/:id/$', 'data', function(req) {
     var id = req.params.id;