This adds AES256 test of encryption and decryption - an example
on how the Encrypt and Decrypt classes are used.
Also add a convenience function for Hash, accepting vector of
bytes as this is used in a lot of places.
Change-Id: I9b395c7afb8fac45cae8d7d8bd983f5daaafd64b
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/176887
Tested-by: Jenkins
Reviewed-by: Tomaž Vajngerl <quikee@gmail.com>
