Review $all vs $anonymous behaviour

[dlouzan]

In light of the clarifications supplied by the verdaccio team for issue https://github.com/verdaccio/verdaccio/issues/1120, we should review how we treat the default behaviour of $all and $anonymous.

Upgraded documentation in verdaccio:

• https://github.com/verdaccio/website/issues/46
• https://verdaccio.org/docs/en/authentification#understanding-groups