Properly support all RSA ciphers

[taylorconor]

trafficstars

Currently there is no support for ciphers which require an IV. In rsa.cpp we call EVP_get_cipherbyname to convert the user-specified cipher name into an OpenSSL EVP_CIPHER. If this EVP_CIPHER is one which requires more than just a password (one that also requires an IV) the encryption will fail.

DoD: RSA::write_to_file supports all ciphers in EVP_get_cipherbyname, and there are tests for this in rsa_test.cpp.