call `loaded` processing hook after collections were loaded; add new Vuex action 'loadWithCollections' for loading instance and collections by one function

The 'loadWithCollections' action is necessary for the correct working of the loaded hook. This hook should be called after loading of collections since:

• we can need to use collection's items in the loaded hook;
• load and loadCollections called in pairs in several places;
• we don't have an appropriate common hook that will be always called after inital loading or refreshing the instance and collections.