Revert "Drop /map_metadata API entry point"

This reverts commit b37b07a06a1dd3cf05d60f4aa613ab5c48b90700.

This was too light of a decision...

lib/cartodb/cartodb_windshaft.js

@@ -55,6 +55,26 @@ var CartodbWindshaft = function(serverOptions) {
     });
 
 
+    /**
+     * Helper to allow access to metadata to be used in embedded maps.
+     */
+    ws.get(serverOptions.base_url + '/map_metadata', function(req, res){
+        ws.doCORS(res);
+        Step(
+            function(){
+                serverOptions.getMapMetadata(req, this);
+            },
+            function(err, data){
+                if (err){
+                    ws.sendError(res, {error: err.message}, 500, 'GET MAP_METADATA');
+                    //res.send(err.message, 500);
+                } else {
+                    res.send({map_metadata: data}, 200);
+                }
+            }
+        );
+    });
+
     /**
      * Helper API to allow per table tile cache (and sql cache) to be invalidated remotely.
      * TODO: Move?

lib/cartodb/server_options.js

@@ -550,6 +550,25 @@ module.exports = function(){
         );
     };
 
+    /**
+     * Little helper method to get map metadata and return to client
+     * @param req
+     * @param callback
+     */
+    me.getMapMetadata = function(req, callback){
+        var that = this;
+
+        Step(
+            function(){
+                that.req2params(req, this);
+            },
+            function(err, data){
+                if (err) callback(err, null);
+                else cartoData.getMapMetadata(data, callback);
+            }
+        );
+    };
+
     /**
      * Helper to clear out tile cache on request
      * @param req