This PR attempts to better inform people about the problem identified at https://community.letsencrypt.org/t/certbot-auto-deployment-best-practices/91979/.
I was hesitant to add the flag --no-permissions-check, however, if there's some obscure distro out there (or custom user setup) that has a strange users and groups, I didn't want us to either:
Have to put out a bug fix release
Refuse to fix the problem and let them deal with warnings on every run
* add check_permissions.py
* Update letsencrypt-auto.template.
* build letsencrypt-auto
* Add test_permissions_warnings to auto_test
* Allow uid/gid < 1000.
* Add --no-permissions-check to Certbot.
* Add --no-permissions-check to certbot-auto.
* Add test farm test that letsencrypt-auto is quiet.
As a bonus, this new test will catch problems like the one that the caused
0.33.1 point release.
* Update CHANGELOG about permissions check.
* Update permissions comment.
* Fix symlink handling.
* Use a better default in auto_test.py.
