Clean up Waterman / Cahill

[Fil]

The issue is described here: d3/d3-geo-projection#125

To sum up this would need to:

• introduce geoCahill1909 (which would be geoPolyhedralWaterman but with the inferior choice of angles from Cahill's original — and that could be a parameter of course), and be mindful of the face projection used in 1909
• create a "true" geoWaterman with Antarctica cut out (see also [Cahill-Keyes] Re-assemble and attach Antarctica  #11)
• obsolete geoPolyhedralWaterman

[Fil]

A first draft of the Waterman here
https://beta.observablehq.com/d/6c32c18bb8550021

[Fil]

new draft here
https://beta.observablehq.com/d/8085f693f9972f0e

[Fil]

For the moment I don't see very well how the Antarctica piece is made in Steve Waterman's original — the angles and the parallels in my draft are not the same as in the original.