Wrong links / references in doc

The link to configuration at experiment options config command points to a non-existing page (:ref:clapper.config). ReadTheDocs returns a 404 error page.

This link should point to clapper.config instead. The :ref: directive is either not needed, or requires to be placed before the whole link text (To be tested).

P.S. Another link also returns a 404 error:

• link to global configuration in https://clapper.readthedocs.io/en/v1.0.1/click.html#global-configuration-rc-command-group;