* Extract it into the "encryption_scheme" service.
* Make these engines to use the service, remove duplicate code.
* Change MY_AES_xxx error codes, to return them safely
from encryption_scheme_encrypt/decrypt without conflicting
with ENCRYPTION_SCHEME_KEY_INVALID error
* no --encryption-algorithm option anymore
* encrypt/decrypt methods in the encryption plugin
* ecnrypt/decrypt methods in the encryption_km service
* file_km plugin has --file-key-management-encryption-algorithm
* debug_km always uses aes_cbc
* example_km changes between aes_cbc and aes_ecb for different key versions
