Remove CP-1252 cleartext signature unit-test
Fix key expiration time. Add key revocation unit test.
Verify V3 certification signatures
Merge readPublicKey for V3 and V4
Support multiple keys per ASCII armored block. Unify error handling: replace print_error function
with exceptions. The idea is to use exceptions internally, but catch them in the high level API
functions and return errors as implemented in openpgp.key.readArmored.
Refactoring Key class to use structured data. Transform key from-to packetlist.
Add User and SubKey class. Verification methods for key components.