User preferences

[leafo]

An abstraction on top of QSettings should be made with methods for common actions for saved data:

• Logging in, the API key should be cached into user settings, password does not need to be stored
• Whether to automatically check for updates
• Whether to show desktop notifications

A settings dialog will probably need to be created with a few toggles.

[leafo]

New API call to get info about current user:

GET /api/1/:api_key/me

{  
  user:{  
    url:"http://leafo.itch.io",
    username:"leafo",
    id:1,
    cover_url:"http://img.itch.io/aW1hZ2UyL3VzZXIvMS8zODEzNi5wbmc=/100x100%23/fsSoF5.png"
  }
}