Self-signed certificate generation using Onionmine

Description

Right now the generate-selected-cert command only creates the private key and the certificate request. It would be good if it also created a self-signed certificate.

Then, onionsite operators could choose whether to get a CA-signed certificate or use the self-signed cert. Then could even start using the self-signed cert for a while and then get a CA-signed cert.

This would be useful for the onionspray create command as well.

Tasks

• Update the generate-selected-cert to also create a self-signed certificate.
• Test the self-signed certificate.
• Documentation update (tutorial and usage pages).

Time estimation

• Complexity: very small (0.5 day)
• Uncertainty: low (x1.1)
• Reference (adapted)