added example server setup page, links from README and How-do-I-run-my-o...

added page describing server setup using PowerDNS + DNSChain + Namecoin on Debian 7

similar to page on my blog, but no mention of Emercoin, and I added .eth and .p2p extensions to PowerDNS config directive

also changed the reference in README page, and linked from How-do-I-run-my-own.md

It may be better to simply link to the corresponding file in the `scripts/` folder? Or at least mention that we provide this. (Same for `namecoin.service`).