[Documentation] DOM TS FAQ

As we are finalizing the DOM TS framework, I've updated the DOM TS pages at
W3C (http://www.w3.org/DOM/Test). Please review.

Also, anticipating people to join in, I've started writing a FAQ, which you
are invited to sanitycheck and check for things that are missing.

/Dimitris

 <<DOMTSFAQ.html>>