Implement configuration "diff" against stored baseline

This feature combines data from the current stored configuration baseline and/or new configuration files to create a merged model of configuration, then compares this against the effective configuration as stored in the JCR. These differences should be available as a new object model for multiple uses.

1. Export the diff directly as new YAML namespace, cnd, and config definitions. Ideally, this could form the basis of a "diff export" CMS console feature. The definitions would be represented as effectively a new module.
2. Display some form of summary report for diagnosing conflicts between the current config and incoming definitions from an upgrade.

An open question is how to determine "interesting paths" for configuration, which could come from the current auto-export module configuration, some kind of hard-coded rule, a new type of configuration, or to be specified explicitly on invocation.