0.5.0: Encryption and multipacket responses

Improvements:

• Encryption.
• Multipacket responses.
• More error handling and stability corrections.
• Smaller stack pressure.
• Serialize state in CBOR.
• Make default location external.
• Encapsulate internal implementation.
• Handle state writing and deserialization errors.
• Use smaller buffers where possible.
• Decrease write pressure by accessing state RO.

Required for the use with the updated OTP client in pynitrokey (since v0.4.33).