Added support of albums and music on wall to VkService. Fixed update bugs.

Fixed LazyPopulate called twice when we try to click update in context menu for item before it's populated.
Fixed Clementine crash when we try to update root item while one of its children in updating process.
Make this a ternary expression:
```cpp
QStandardItem* item = current.data(...) ? model()->itemFromIndex(current.parent()) : model()->itemFromIndex(current);
```