Move reusable validation factory semantics to a common super class

This is in preparation for creating a BindingsValidatorFactory. The
common super class removes the need for copying behavior from the
current ValidatorFactory.
Fix structure of require statements to make binder package loadable

With this commit, all pops related files are required in the
pops.rb file. The types.rb was removed since it was no longer
needed.
Merge pull request #26 from thallgren/feature/binder

Make changes to enable working on binder checker/validator