Button to "select all codelists"

[Robsteranium]

This would allow you to see all the datasets that involved a given facet (i.e. "I need a geographic breakdown but I don't care which scheme is used") and would help lead users to a comparison view more quickly (helping to demonstrate how the tool works).

Why not turn on all facets/ codelists from the outset? This would present an overwhelming amount of information and would exclude some datasets that don't fit into the facet configuration (although perhaps this actually suggestions a mismatch between the facet configuration and the family scope).

An alternative might be to have this selection be the default when you open a facet but that wouldn't play nicely with auto-applying facets (#50) as the no-action default would be to make a selection (so you'd have to deliberately reset to cancel) - that'd be frustrating if you were just having a look.