Replace EHS with something more modern

[sbx320]

The EHS web server we use is ancient (~2008) and contains a decent amount of bugs and performance issues. As it has not been maintained for a long time and pulls in some further dependencies as well, we should get rid of it.

My suggestion would be using boost::beast (https://github.com/boostorg/beast) for it, as it's quite modern and I also have some experience in working with it. As an added benefit we'd also get HTTPS support and even Websockets (not sure if those would be useful at all for us).

[qaisjp]

Sounds good to me.