[#1644] using Codec.hexSHA1() to hash the urlcache key

To avoid hitting the memcache max key length limit (250 chars) for the URL cache (@CacheFor).

More about this in the ticket: https://play.lighthouseapp.com/projects/57987-play-framework/tickets/1644-cachefor-hitting-memcache-key-length-limit

If possible, I'd like to see this also in the 1.2 branch.