Include full $name of the derivation into docdir, so documentation for
python package "foo" is installed into $out/share/doc/python3.10-foo-1.2.3
instead of just $out/share/doc/foo, where it may conflict with some
other package named "foo" and not-coinstallable with different
versions of the same python package.
Change from $name to $pname was introduced in [1ee5fca], probably as
unindented side-effect of adding support for formats other than html.
Removes the up until now unused option to specify a `sphinxOutdir` in
favor of allowing to specify multiple builders, which is for example
useful for generating both documentation and manpages using the hook.
Since the output path cannot be determined from within the package we
automatically generate it and add a diversion for manpages, so they land
in the correct output and path.
