Local ip check update

[foxmcloud555]

We need to establish a websocket connection between two devices connected to the same mobile hotspot.

This means we can't reliably get a valid DNS entry for the isLocal check.

I have just added extension that will return true if a supplied IP is within the Private ranges.

[kijz]

tested this today and also saved me a lot of trouble, while trying to connect via iOS on a local network (no internet).

var name = System.Net.Dns.GetHostName ();
var addrs = System.Net.Dns.GetHostAddresses (name);

would never return the ip address in the local network, which you can view via Wifi (i) icon.
Worked on android though.

[MerijnHendriks]

Thanks for the commit, it really helped me out! You probably do want to update the pull request to use the same styling as the rest of the codebase.