Rework the manual and how it is generated

[fingolfin]

Generate the main page and title page with AutoDoc instead of keeping a
handwritten doc/manual.xml.

Drop the copyright line, which has little legal value. Instead,
say in Section 1.1 where the data comes from and who played which
role. The README now points at the manual instead of repeating any
of this.

Say how the groups are really named. The manual claimed they all use
ATLAS notation, but that is manifestly not true.

Assisted-by: Claude Code (Opus 5)

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.35%. Comparing base (2e188b8) to head (88a3ed0).

Additional details and impacted files

@@           Coverage Diff           @@
##           master      #99   +/-   ##
=======================================
  Coverage   99.35%   99.35%           
=======================================
  Files          52       52           
  Lines       44830    44830           
=======================================
  Hits        44541    44541           
  Misses        289      289           

Files with missing lines	Coverage Δ
lib/primitiv.gd	100.00% <ø> (ø)

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