Add autoreject_file support to minion authentication

This commit adds support for a file similar to autosign_file, which can
be used to automatically reject minions which match the expressions
inside it.
prepend root_dir to autoreject_file
Add autoreject_file to master config template
Add autoreject_file to master config file documentation

Included a versionadded directive to note when this was added, to reduce
confusion.
First attempt at abstracting ZeroMQ communication.
Complete abstraction of ZeroMQ.
Starting on unit tests for docker and salt.utils.
Work on salt.utils unit testing.
Pylint fixes for regex errors.
More utils testing.
Fix regression in postgres module.

Closes #9372
Updated doc title to reflect actual module name

Refs #9366
Merge pull request #9380 from cachedout/#9372

Fix regression in postgres module.
Many more unit tests for salt.utils

Small doc change.
Merge pull request #9382 from cachedout/docker-unit-tests

Unit testing
Update unit test to match PG fix.
Merge pull request #9383 from cachedout/postgres-unit-test-fix

Update unit test to match PG fix.
Line fixes
incron state: rm unused import

************* Module salt.states.incron
salt/states/incron.py:44: [W0611(unused-import), ] Unused import os
salt/states/incron.py:47: [W0611(unused-import), ] Unused import salt
salt/states/incron.py:49: [W0611(unused-import), ] Unused import _needs_change
incron module: rm unused import of random

************* Module salt.modules.incron
salt/modules/incron.py:9: [W0611(unused-import), ] Unused import random