Use augeastprovider, not augeasproviders

This is a fork/snapshot where the core mixin has been separated from the
included implementations.
Remove supplamentary module installation code

It's causing more trouble than it's worth. We want a single source of
truth to define which modules are necessary, and during development at
least that should be the Puppetfile. Having module names and versiones
defined in the alternate installer script just introduces confusion as
the versions fall out of date.