Adding support for better AES Transformations that use an IV

The old  Crypto APIs did not support AES transformations, which require the use of the IV in the decryptAES(..)
Hence if you used a transformation that looked like AES/CBC/PKCS5Padding decryptAES(...) would fail.
Add notes about migrating to older versions of Play for Crypto APIs
Fix tests for old AES encryption/decryption, and update migration docs.
Switch to AES/CTR/NoPadding, and use a different version to represent encoded strings with IV