DOCS-19. Makes docs navigable by component and version.

This change makes it easier to navigate our docs based on component and version. This should be pushed to a new branch that work in prep for the kiji-mr release is done on. 

The user guide landing page is broken (at least links), because it does not use the templating that is setup for every other page. I created DOCS-18 to address that. It should be a <10 min change.