Added support for HTTPS on local server

[PaoloPia]

As we agreed on https://github.com/pnp/generator-teams/issues/186, I added support for HTTPS including the generation of a self-signed certificate with selfsigned npm package. I also added support for a PFX file + password option, in case the developer wants to use it. This PR requires changes both in generator-teams and yoteams-builder-core. Last but not least, in order to support HTTPS with end-to-end TLS using ngrok there is the requirement to have Pro or Business plan of ngrok.