Add secure_hash base class.
Add header.
Accept char const* for hash() input, as it's more common.
Make identity hold a shared_ptr to key, fixes memory leak.
Update sign_key doxygen documentation.
Update identity doxygen documentation. Add construction from various types.
Access size() directly from peer_id.
Clean up debug output.
Use endpoint type EID as a peer location hint.
Add identity tests stub.