BROOKLYN-55 

* simplify the deployment of the site to apache.org
* restructure a bit installation and getting started guide
This page nominally belongs to the "get started" nav category, but this table is sending links to both the "what is brooklyn" and "get started" categories, and external links - this is an inconsistent navigation hierarchy. Please be consistent about which category pages belong to, and define the hierarchy in the YAML front matter section - see [community/index.md](https://raw.githubusercontent.com/apache/incubator-brooklyn-site/master/community/index.md) and [community/index.html](https://brooklyn.incubator.apache.org/community/) for an example of how to define the submenus.