[sr-dev] more Kamailio into RTC Quickstart

I've put the DocBook source code of the RTC Quickstart guide onto Github. It currently includes some basic information about Kamailio, is there anybody who would like to help expand it? http://rtcquickstart.org/guide/multi/sip-proxy-kamailio.html https://github.com/opentelecoms-org/RTCQuickstartGuide/blob/master/sip-prox… The goal of this document is to show people things that they can do to set up federated SIP just using packages on the Linux distributions. A lot of things like firewall, DNS and certificate creation are covered in earlier chapters too, so the Kamailio section doesn't have to repeat any of that. Regards, Daniel