Set aside original Installfest material
Bring over Downloads and Installfest pages from Boston

We're going to temporarily replace the original Installfest material with the
Boston version, which involves setting up virtual machines.
Bring over styles for installation-by-OS tables
Use shorthand Markdown file extension
Put Downloads under Setup section in top nav links
Add Decklin's Command Line slides
Clean up Downloads and Installfest content

This includes:
* Updating Titleizer class to handle hypenated file names and other acronyms
* Rearrange some content for better flow now that we have a sidebar nav to
outline steps
* Modifying link syntax to determine where a page is part of the flow or
extraneous/optional (HTML vs. Markdown) since sidebar is auto-generated