Use the new disks api to explicitly get the apps data disk stats

We can add the other graphs if the disks deviate later

Also this is still pending the check if symlinked folders are reported
correctly.

Fixes #290

webadmin/src/js/client.js

@@ -761,6 +761,13 @@ angular.module('Application').service('Client', ['$http', 'md5', 'Notification',
         }).error(defaultErrorHandler(callback));
     };
 
+    Client.prototype.disks = function (callback) {
+        get('/api/v1/cloudron/disks').success(function (data, status) {
+            if (status !== 200 || typeof data !== 'object') return callback(new ClientError(status, data));
+            callback(null, data);
+        }).error(defaultErrorHandler(callback));
+    };
+
     Client.prototype.graphs = function (targets, from, callback) {
         var config = {
             params: {