Error handling improvements

[erhant]

• Uses eyre instead of custom NodeResult class, resolves chore: use eyre for error handling #73
• Return error response to the network, instead of just logging, resolves feat: return errors as result with success: false #112
• Return version information within the response, (finishes what include entire p2p message #117 started)
• Lots of sanitizations, refactors and prettifies.
• Removed redundant and unused code pieces.
• Bump version to 0.2.6
• Much more pretty tests, especially for the DKNMessage struct
• Better MessageId function, now prints proper hex instead of weird byte values

Errors are printed in a much better way with eyre debug prints now. Furthermore, if there is a workflow error, it is reported back to DKN with the task id, so that it can be retried.