Added placeholders for privacy recommendations for implementers and location recipients

Hi,

As agreed at the f2f meeting in London, I have added the placeholders
for the privacy recommendations aimed at implementers and location
recipients. This concludes the set of edits that needed to be done
before we could move to FPWD.

http://dev.w3.org/geo/api/spec-source.html (Section 3: Security and
privacy considerations)

Thanks,
Andrei