* DOC: rreword much of the howto-docs guide

DOC: Point Contributing page to new NEP 45

Per gh-16500, changed link style to :ref:`<NEPxx>`.

Added a NEP45 target to NEP 45, and added a NEP29 target
to NEP 29 since it has the irregular NEP0029 target.

The two new NEP targets aren't picked up, though the
older ones are. Tried make clean in neps and docs.

```
  /home/bjn/numpy_git/numpy-1/doc/source/dev/index.rst:191: WARNING: undefined label: nep45 (if the link has no caption the label must precede a section header)
  HOWTO_RELEASE.rst.txt:43: WARNING: undefined label: nep29 (if the link has no caption the label must precede a section header)
  HOWTO_RELEASE.rst.txt:50: WARNING: undefined label: nep29 (if the link has no caption the label must precede a section header)
```

The nep objects.inv does seem to have both the nep29 and nep44 targets.

* DOC: Fixes for 18 broken links

This, with PR #16465, should fix nearly all the remaining broken links
on the site. 4 or 5 others should be easy to fix and just
need attention from someone more knowledgeable -- will
open an issue. For release notes with dead links,
I could usually find links on archive.org for roughly contemporary
versions.

* DOC: Update to "Fixes for 18 broken links #16472"

* Obsolete links, previously commented out, now deleted:
https://github.com/numpy/numpy/pull/16472#discussion_r433928958

* Semantic markup for reference to Python class:
https://github.com/numpy/numpy/pull/16472#discussion_r433553928

* Missing :ref: in internal link:
https://github.com/numpy/numpy/pull/16472#discussion_r433554484

Not included: Resolution on using external/internal doc link in .py:
https://github.com/numpy/numpy/pull/16472#discussion_r433554824

* DOC: Add internal link for 'Fixes for 18 broken links' PR #16472

Making reference [1] an internal link in function_base.py => numpy.vectorize.html

* DOC: Redirect 2 link fixes in PR #16472

* governance.rst link reverted
* ununcs.rst `overridden` link goes where it was meant to


per https://github.com/numpy/numpy/pull/16472#pullrequestreview-424666070

Per #16500 discussion, adds link updates to PR.
Replaces NEP URLs with intersphinx links in these
files:

* doc/HOWTO_RELEASE.rst.txt
* doc/source/dev/howto-docs.rst
* numpy/doc/dispatch.py
* numpy/lib/format.py

and incorporates @rossbar's #16502 change of `config.py`.