Collect stats during linting

[cidrblock]

For a given project, collect stats about tank count, include, plguins used etc.

These can later be used for:

• test requirements used in run time
• untested plugins e.g. coverage

Anything else we could do here? Thoughts?

[MarkusTeufelberger]

Getting a "linter coverage" report would already be interesting, since it is not always clear if some tasks file that gets only dynamically included somewhere is actually being linted.