A new catalog model and builder

Replace the Puppet::Parser::Compiler and related pieces with a new system for constructing catalogs. Model, Types, Validation, Resources, Parameters, Parameter Values, etc. The agent won't be directly exposed to the new catalog model. The catalog will be transformed into the existing catalog format for other users (puppetdb, rspec-puppet, the agent).

This work will be experimental in 3.6 and the actual catalog system in 4.