Return a suggested expense for a natural language sentence



  1. input
  2. group_id OR friend_id
  3. optional:
    1. autosave

Also optional, it's helpful for us if you also pass in creation_method as quickadd

Return value:

  1. An unsaved expense record (in detailed JSON expense format)
  2. If autosave is set, attempts to save record
  3. valid: is the expense hash that is returned a valid expense?