Add Possibility to Switch Security Provider

[sayseakleng]

Hello there! I'm a fan of this library. It's very helpful.
Anyway, I come across that there should be a possibility to switch security provider as in JCE allows this as the following:

val cipher = Cipher.getInstance(DEFAULT_TRANSFORMATION, new BouncyCastleProvider());
cipher.init(Cipher.ENCRYPT_MODE, loadPublicKey(publicKey));

I really appreciate your contribution to this library.
Looks forward to getting this on a future release.

Best Regard,

Reno