Out of date even for v3, and supplanted by v4 architecture page.

Remove some old content
Generally refresh

Currently we have 'All Hooks' followed by each of the categories of hooks
so it looks like 'Setup' is a hook category.  Its content is closer to 'Using Hooks'

These documents are misleading -- they talk about CiviMail because, *historically*,
much of this grew out of CiviMail. However, *today*, tokens are used more generally.
Also, in `civicrm-core`, `TokenProcessor` is *not* used by CiviMail. (You have to
install FlexMailer to use it.)

style guide ref:
https://docs.civicrm.org/dev/en/latest/documentation/style-guide/#hackable-urls

I'd like to be able to merge the general, incremental improvements for the
"Testing" section, but these two new pages aren't yet written.  Comment them
out.

1. Add new entries for Protractor, Codeception, and QUnit

2.  This menu includes (a) some pages about the overall testing process and
(b) some pages about specific tools.  Consistently put the general before
the specific.