(PUP-3312) Remove deprecated methods from the Puppet module

This commit removes the `parse_config` and
`initialize_settings_for_run_mode` class methods from the Puppet
module. This commit is part of the code removal effort for Puppet 4.
(PUP-2733) Refactor binder's use of Puppetx

This refactors the binder's use of Puppetx. The problem with the
previous implementation was that it squatted on the Puppetx namespace in
a way that made it difficult to use for its original purpose.

This commit changes the organization. The extension points that define
how puppet can be extended are in Puppet:Spi namespaced modules. One
module per extension. Each such extension specifies the type and the
symbols to use when binding services.

A Puppet::Spi::Configuration is responsible for configuring/wiring
the service programming interface(s) by registering them for inclusion
in the binder(s) being set up.

The only currently existing implementation of a default service is
the Json syntax checker - it has also moved out from the Puppetx
namespace and is now found in Puppet::SyntaxCheckers::Json.
(PUP-2733) Rename puppet::spi to puppet::plugins
(PUP-2733) Cleanup names that contained SPI and touch up comments
(PUP-3293) Remove deprecated and unused pson and rubygems features

This commit removes the deprecated `features.pson?` and `features.rubygems?`
features.
Merge pull request #3283 from whopper/pup-3293/removal/pson-rubygems

(PUP-3293) Remove deprecated and unused pson and rubygems features
Merge pull request #3284 from whopper/pup-3312/removal/puppet-module

(PUP-3312) Remove deprecated methods from the Puppet module
(PUP-2366) Use EL 7 masters for Windows acceptance

Prior to this commit, our Windows acceptance tests used RHEL 6 masters,
which ship with Ruby 1.8.7. As part of PUP-2366, we need to bump these to
EL 7 to make use of a newer Ruby. We would also periodically run into
issues where there was a transient failure on the master that caused the
Windows acceptance job to fail.

This commit modifies all the Windows Beaker node configs to use RHEL 7
masters.
Merge pull request #3294 from rji/issue/master/pup-862-use-rhel7-masters-for-windows

(PUP-2366) Use EL 7 masters for Windows acceptance
(MAINT) Add debug log messages for env caching

This commit just adds a couple of debug-level log messages that
provide some insight into when environments are cached, and
when the cache entries are evicted.
Merge pull request #3296 from cprice404/maint/master/debug-log-messages-re-env-caching

(MAINT) Add debug log messages for env caching
Merge pull request #3286 from hlindberg/PUP-2733_rename_spi_to_plugins

(PUP-2733) Refactor the Binder's use of Puppetx