(packaging) Update template task for new erb_file method

The packaging repo will have all utilities split out into different classes for
sanity's sake, and one of the tools that got an overhaul is erb. This commit
updates puppetdb to use the new utility.
(packaging) Update top-level Rakefile's version and pe determination

Prior to the commit, the versioning in puppetdb would fail from a rake
perspective if the packaging repo wasn't present. This commit updates it to
fall back to git describe and if that fails to a hardcoded string, so that we
always have a version. We also set the @version variable to
Pkg::Config.version, which is how we access data provided by the packaging repo
in the new library-format.

Signed-off-by: Moses Mendoza <moses@puppetlabs.com>
(packaging) Fully qualify variables supplied by the packaging repo in templates

Part of the variable scoping overhaul within the packaging repo was ensuring
the data about builds lives inside module Pkg::Config. In other projects, we
only use variables set by the packaging repo in templates, which means we can
pass the binding of the packaging repo Pkg::Config class into the template
engine and keep using "@" variables like we always have. But in puppetdb, we
mix data supplied by the packaging repo and data supplied by puppetdb itself in
the same template, which means we can't use just the Pkg::Config scope. Since
there are far more variables supplied by puppetdb in the templates than the
packaging repo, we opt to use the puppetdb scope and fully qualify access to
the variables supplied by the packaging repo, by referencing them as
Pkg::Config wherever we use them.

Signed-off-by: Moses Mendoza <moses@puppetlabs.com>
redirect to moses - remove this commit
(packaging) set project to pe-puppetdb when building pe-puppetdb

Until we split out the packaging of pe-puppetdb from puppetdb, with the new
packaging system we need to explicitly tell the automation that the project
we're building is called 'pe-puppetdb' instead of 'puppetdb.'

Signed-off-by: Moses Mendoza <moses@puppetlabs.com>