added a method to easily initialize a PkiPrivateKey based on an SDK UaPkiPrivateKey, and befriend the class with PkiRsaKeyPair so the latter can easily access the internal SDK instance
added a method to easily initialize a PkiPublicKey based on an SDK UaPkiPublicKey, and befriend the class with PkiRsaKeyPair so the latter can easily access the internal SDK instance
added support for PkiRsaKeyPair