Restore a compact version of "Datalib" pages?

[fingolfin]

We remove https://web.archive.org/web/20220626194259/https://gap-system.org/Datalib/datalib.html and its subpages.

Perhaps we should add back a page https://www.gap-system.org/capabilities/datalib which copies / condenses some of that old information; then we can redirect the old removed URLs to that.

(Of course the new page should also be linked to suitably from https://www.gap-system.org/capabilities/)