(FACT-569) Run Facter acceptance against Ruby 2.0 x64 on Windows

This PR refactors and otherwise improves our ability to run Facter acceptance tests on Windows.
- (FACT-569) refactor windows acceptance nodesets
- (FACT-569) refactor non-windows acceptance testing nodesets
- (FACT-569) append `$ruby_arch` to `$platform` only if running on Windows
- (FACT-569) fix permissions for `/bin` directory for Ruby on Windows

Once this PR lands in stable, we'll update our Jenkins jobs accordingly. For an example of this in action, see the following (temporary) Jenkins job, [Facter-Acceptance-Windows-ng](https://jenkins.puppetlabs.com/job/Facter-Acceptance-Windows-ng/)
I'm curious if this will cause adverse side effects.