REST resource that selects the subtitle for a release / watchlist item

[bdunogier]

Required by #13 to select a new subtitle

For a given release that matches a watchlist item, saves the given subtitle for the episode. If any, the existing subtitle is replaced.

The chosen subtitle is marked as manually chosen for the episode (specific status ?).

h4. Possible API

PUT /watchlist/release

{
  "subtitle": "subtitle-url"
}

This needs to be improved...