HTTPS: Support Secure extension for HTTP

[annoviko]

Is your feature request related to a problem? Please describe.
Right now there is only HTTP server without ability to use secure extension using SSL or TLS. But there is need to test clients that uses HTTPS protocol for communication.

Describe the solution you'd like

• Provide RobotFramework API to configure HTTP to work through SSL or TLS (enable HTTPS support).
• User should be able to specify a certificate for the server and for the client.
• User should be able to specify a private key for the server and for the client.

Describe alternatives you've considered
Maybe separate HTTPS server library, but it will reuse a lot of functionality from HTTP.

Additional context
N/A

[Linusoderlind]

Have you made any progress on this?

Otherwise I will take a stab at it.