update Vagrant file to conditionally create symlink

on the build server, it was trying to create
symlinks even when they already existed.

This led to failures when provision was run (after
the initial boot). This adds some extra code so
that we only attempt to add the templates symlink
if it does not already exist.
add site.pp

Adds my working site.pp. This should not be here for forever, but
adding it here temporarily makes testing a bit easier.