Support tracking of sub-wikis from one configuration in the main wiki admin

[aubincleme]

Many deployments of XWiki instances don't come with just one main wiki, but with multiple sub-wikis. The analytics application should provide a way for administrators to enable tracking of analytics on all wikis (main & sub-wikis).

This would also enable the analytics application to be a complete replacement of the existing Matomo application, which provides this feature.