Be compatible with HTTP/2

[mildred]

devd has the ability to serve content with TLS, it would be nice if HTTP/2 was enabled in that case to allow browsers to use it and benefit from it. This is useful for development environment to test how an app reacts to it.

[leg100]

Freakish timing! I was going to raise the same issue today - I've run into the dreaded HTTP/1.1 maximum of 6 open connections. HTTP/2 defaults to 100.