Implemented self-signed certificate generation for HTTPS

[samj]

In support of @robertbinning's PR #33 I have implemented self-signed certificate generation in PR #49 so we can turn on HTTPS support (port 8443 now instead of 3080) out of the box

We should go on and implement Let's Encrypt so folks can easily host their own servers on publicly-accessible (i.e., verifiable) domain names (e.g., paios.example.com).

I've also tweaked frontend/dist so it has a 404.html to tell you why the frontend isn't available (e.g., hasn't been built, isn't running on a dev server, isn't the canary branch, etc.).

[samj]

@pjbedard you're welcome to check this out as well if you like.

[samj]

Thanks @quaid for the input. I've merged #49 into develop.