Store and parse BLISS private and public keys in DER and PEM format

Additionally generate SHA-1 fingerprints of raw BLISS subjectPublicKey
and subjectPublicKeyInfo objects.

Some basic functions used by the bliss_public_key class are shared
with the bliss_private_key class.

src/libstrongswan/credentials/cred_encoding.h

@@ -144,6 +144,10 @@ enum cred_encoding_part_t {
 	CRED_PART_PKCS10_ASN1_DER,
 	/** a PGP encoded certificate */
 	CRED_PART_PGP_CERT,
+	/** a DER encoded BLISS public key */
+	CRED_PART_BLISS_PUB_ASN1_DER,
+	/** a DER encoded BLISS private key */
+	CRED_PART_BLISS_PRIV_ASN1_DER,
 
 	CRED_PART_END,
 };