Redmine#3283: tag everything

See https://cfengine.com/dev/issues/3283 for planning details

This PR has several pieces for review:

* add functions to give tags to any newly created class or variable
* fix acceptance tests for `variablesmatching` and `classesmatching`
* verbose-log the new set of tags whenever a variable or a class are tagged
* tag all classes and variables created in C

The last one is a big commit and is my preliminary idea.  I expect it will be changing significantly but at least we have a starting point and I've found every place in code that needs to be tagged.