Include nautilus-gtkhash

Originally created by @alant on #6763 (Redmine)

nautilus-gtkhash is a “nautilus extension for computing checksums and more using”

“The GtkHash extension for nautilus which allows users to compute message digests or checksums using the mhash library. Currently supported hash functions include MD5, MD6, SHA1, SHA256, SHA512, RIPEMD, TIGER and WHIRLPOOL.”

It is available in wheezy debian repositories

Feature Branch: feature/6763-include-nautilus-gtkhash

To upload designs, you'll need to enable LFS and have an admin enable hashed storage. More information