Docs: "Ellipsoids" page lists only 10 ellipsoids, while proj -le lists 46 ones

[agiudiceandrea]

The "Built-in ellipsoid definitions" section of the "Ellipsoids" page lists the following 10 ellipsoids' definitions

ellps	Parameters	Datum name
GRS80	a=6378137.0 rf=298.257222101	GRS 1980(IUGG, 1980)
airy	a=6377563.396 b=6356256.910	Airy 1830
bessel	a=6377397.155 rf=299.1528128	Bessel 1841
clrk66	a=6378206.4 b=6356583.8	Clarke 1866
intl	a=6378388.0 rf=297.	International 1909 (Hayford)
WGS60	a=6378165.0 rf=298.3	WGS 60
WGS66	a=6378145.0 rf=298.25	WGS 66
WGS72	a=6378135.0 rf=298.26	WGS 72
WGS84	a=6378137.0 rf=298.257223563	WGS 84
sphere	a=6370997.0 b=6370997.0	Normal Sphere (r=6370997)

while the proj -le output contains 46 ellipsoids's definitions.

[mwtoews]

Related to #4053 where we may want to display something like "Note that the following list is no longer updated, and some values may conflict with other sources" above the table. I was going to get around to this at some stage...