Add REST-Method to ARE that returns the current local IP address, for FAQ

[klues]

FAQ 38 (see: https://asterics.github.io/AsTeRICS-Ergo/mock.html#!/home/envcontrol/help/faq/38) currently uses a Javascript-Hack in order to get the current local IP-address. However it only works in chrome and Firefox, not in IE or Edge.

In order to show correct info in this FAQ also in IE/Edge we would need a ARE-Rest method that returns the current local IP address.

[klues]

in order to also support Edge/IE for showing the correct local IP in the Smartphone-FAQ, we maybe could add a REST-method that returns the current local IP, with some snippet like this:

Enumeration< NetworkInterface > interfaces = NetworkInterface.getNetworkInterfaces( );
List<NetworkInterface> list = new ArrayList<>();
while(interfaces.hasMoreElements()) {
    NetworkInterface element = interfaces.nextElement();
    if(element.isUp() && element.getName().startsWith("wlan")) {
        list.add(element);
    }
}
list.get(0).getInetAddresses();