Option to store a user generated document

Original idea from https://forum.duniter.org/t/re-emission-dune-transaction/8161

• option format: --store/-s --file/-f=<path>
  • #305: tx: would allow to send (by any messaging mean) the document to someone else to sign it for multi-sig: #144.
  • cert
  • membership
  • revocation: basic feature of this command
  • identity
• sign: to add a signature to a transaction
• send: new command to send those documents
• ability to resend a document