Add load_overrides method for PARAMS_FILE overrides

Several workflows rely on being able to supply an optional yaml
parameters file that overrides all set values with its data. This has
always been supplied as an environment variable, "PARAMS_FILE." To
honor this, we have a method in config to override values as
expected.

Signed-off-by: Moses Mendoza <moses@puppetlabs.com>
Add a variable reassignment for pe_name to project

This was in 20_setupextravars.rake, and is used for repos with an identity
crisis, e.g. pe-puppetdb vs puppetdb.

Signed-off-by: Moses Mendoza <moses@puppetlabs.com>
update 20_setupextravars.rake for new librarification

We've moved the variable reassignment of pe_name => project into the
reassignments in the library. We don't need to export all of our instance
variables anymore, because we're using bindings wherever we need them, and
finally we don't have to haphazardly use a bunch of manual environment variable
overrides - we have a method for that now.

Signed-off-by: Moses Mendoza <moses@puppetlabs.com>
Replace all occurrences of @build. with Pkg::Config

Except for the few methods of @build, which were params, set_params_from_hash,
params_to_yaml, print_params, and set_params_from_yaml, which are replaced with
their correspending Pkg::Config methods.

Signed-off-by: Moses Mendoza <moses@puppetlabs.com>
Remove 10_setupvars.rake, this is handled by config now
Rename to 20_setupextravars to load_extras, since that's all it does now
Build.rake is now only the build from params rake task

All the other facilities are done by Pkg::Config.

Signed-off-by: Moses Mendoza <moses@puppetlabs.com>
Remove template.rake, this functionality  is now provided by the tar lib