Add version and impl info field to EncryptedKey

This change alters the EncryptedKey struct to provide the ability to
version the KDF used to derive the key to wrap the EncryptedKey with.
Additionally, it adds an addl_info field to allow the implementor to
specify any other information they would like to attach to the key
structure.

Test: tbd
Change-Id: I1a32556cdff371138118028772b773f5e9b22c61
4 files changed