Improvement reverse proxy: New entry field to add additional settings for virtual hosts

[carsten (Carsten Härle)]

I implemented a solution. Hopefully it makes it into the next release.

Improve reverse proxy, automatic handling of websockets

Many applications use websockets today (e.g. webtop5). The current reverse proxy module of Nethserver only adds ProxyPass and ProxyPassReverse, so Websockets are not passed correctly. The only solution is to not use the reverse proxy UI at all and create manual configurations in /etc/httpd/conf.d instead, which is however complicated and not shown in the UI. Fortunately it is possible to handle websocktets automatically by using the rewrite enginge: E.g. Reverse proxy xy.mydomain host to xy-ba…