Add signHash, validateHash to AsymmetricAlgorithm
Add load, save, fingerprint to AsymmetricAlgorithm
Refactor object signing

The overall object structure has changed. New structure is:

- Header
- PublicBlock
  ...
- PrivateBlock
  ...
- SignatrueBlock
  - Fingerprint of issuers public key
  - Hash of Header, PublicBlock and PrivateBlock
  - Signed Hash
- Hash of Header, PublicBlock, PrivateBlock and SignatureBlock

The new classes from net.secloud.core.crypto are now fully incorporated
into the system.