Implement aggregator CLI commands for configuration parameters

[jpraynaud]

• New aggregator CLI command for configuration parameters:
  • protocol-configuration export-markers which:
    • Read on chain markers
    • Convert the markers to human-readable format
    • Stores markers on disk
  • protocol-configuration import-markers which:
    • Imports the human-readable markers stored in a file
    • Verifies their integrity,
    • Verify if there is conflict with the data stored on chain
    • Encodes the markers in the datum
    • Sign the datum
    • Write a datum file on disk
  • protocol-configuration generate-keypair?