Display option to display the generated document before sending it

Implement --display/-d option for the five send-documents commands. Implement it as a general option that would be used by the five commands: tx, cert, membership, identity, and revocation.

It would display the generated document, and would ask to send it or not. Afterwards, a confirmation prompt ask to send it after a visual check have been performed.

This would allow to be sure we are sending the correct document and it can also be used for debugging and testing purposes.

Tasks

• By-pass prompts?: license approval, send doc confirmation. No, since it would allow to send a document by by-passing them.
• Merge table summary and document display confirmations when this option is passed
• Global option over command-specific options? Would not duplicate five decorators on the five send-documents commands.
• Display the document with and without the signature in case the key is not defined
• In case the document have been signed (key provided), suggest to send the document after displaying it

Commands

• cert
• #88 (closed): membership
• #380 (closed): tx
• #89 (closed): revocation
• #90: identity