Get single post from API by id and query params; Auto-sort posts list

 Get single post from API by id and query params; Auto-sort posts list

closes #2883, closes #2951
- introduce custom findQuery in ApplicationAdapter
- posts/post route and editor/edit route now use custom findQuery to find a single post by id with query params
- create a sorting function in PostsController for out-of-order loading
- refresh updated posts in posts.index to make PostsList highlight latest draft after returning from a save in editor

The only problem I had was after updating a draft.. going back to the PostsRoute highlighted the previously last-updated draft, not the most currently updated one. I had to modify PostsIndexRoute to grab a fresh list from the server, but that causes an extra request on first landing on `/ghost/ember/`.