RCv3, BfV, purge option, some link fixing, updated rev history

Oy! Writing up two, no three, new features at once, plus discovered some WADL weirdness. Anyway, please take a look. I'll also send out a PDF, which you might find easier to peruse.

Added a concept section for Cloud Bursting with RackConnect V3, added info on using loadBalancer config for RCv3, added info on user_data for BfV, addd purge arg for delete server from scaling group.
Trying to learn about Docbook: what does this whitespace change?