Tidy up config example

I found the section on the query params hard to mentally parse. At first
I thought there was a missing example, then I realised it referred to
the section below.

* Added a link to the Icinga query params docs
* Reorganised comments above the line to which they refer
* Added a host param to match the existing comment line
* Removed the whitespace only lines
Merge pull request #5 from alphagov/tidy-up-config-example

Tidy up config example