Move whirr integration

The whirr integration, currently in core brooklyn, isn't well maintained and has not been used at all recently. I wouldn't be surprised if it is therefore currently broken; certainly it would require effort to get it to and keep it at the code quality we want within core brooklyn.

It should really have been moved to its own downstream repo before brooklyn moved into apache. In fact, the code was forked with this intent (prior to the apache move) into https://github.com/brooklyncentral/brooklyn-whirr.

Since being in Apache, there have only been two changes to the whirr integration code: the automated addition of apache license header to every file, and a global refactor (presumably through IDE support) to change the deprecated use of `HttpPollValue` to `HttpToolResponse`.

This PR also tidies some other docs (see first commit) that mentioned Whirr, beyond just deleting the reference.