Kafkacrypto

Another bug fix: ensure chain messages only replace current chain if they validate properly, instead of unconditionally. This was a bug due to differences in exception handling between different parts of the code, so the opportunity was taken to also unify exception handling to help prevent similar bugs in the future.

Two more less critical bugs resolved: make sure no more than one key request per root topic is in flight at once (to avoid ephemeral key clobbering), and that properly signed, but malformed, key management messages do not crash the management thread.

Fix one more high priority bug: incorrect determination of nodeID in the case of a fully standalone configuration file.

This fixes a couple of high priority bugs:
- Improper configuration loading due to case-insensitive keys in ConfigParser. This has been resolved by properly implementing case-insensitive checks while retaining file case sensitivity for proper base64 operation in keys.
- Fix a bug where a combined producer and consumer would respond to its own consumers key requests. Reworked implementation to only respond when the key index requested is available.

This is 0.9.8, with one fix to the kafka-python wrapper code that was missed in the original release.

This release continues to make changes based on security reviews. Major change is a revamp of the chain processing code to be more readable and enable future additions to be made more easily. Major changes include:
1. Implementation of allowlist and denylists. This removes the need for separate code pathways for root of trusts, enabling them to be treated as entries in allowlist.
1. Implementation of automatic processing of messages to adjust allowlists, denylists, and chains. This enables very short chain lifetimes, a security benefit. It also enables a private key to self-sign that it should be revoked.
1. Implementation of a pathlength constraint for further tightening of chains. Minimum usable value is typically 1, unless the end of the chain will not sign any further messages.
1. Fix kafka wrapper poll implementation to make the timeout optional.