Movie: Cache the results for a week.

Cache movies results for 1 week. I initially set it to one month, but I feel that that's too long--especially if people search for new movies such as "guardians of the galaxy movie". 1d is too short (that's the default), so I went with 1 week instead.
It's probably best to cache the results for one day in https://duckduckgo.com/?q=movies (since the movies in theaters probably don't change every minute or every hour so there's no reason for us to disable caching)