Allow packages to be updated on their own

In some cases, it is required to let packages update themselves:
- Some Windows updates increase the version number of installed packages
  while this version cannot be deployed standalone through a regular
  win_repo package
- Allow users to apply timely critical updates on their own so they
  don't have to wait for the admins to provide the newest version (e.g
  auto updates of software such as Mozilla Firefox which allows to
  install updates through regular users without administrative
  permissions)

Fixes #11602
Fixes 12702: now a traceback exc is written when returner fails
auto accept keys in minions_autosign

Accept keyids if a file with the same name is found in minions_autosign.
Also option to check the datestamp of the file and only accept if within timeout.
Improve jinja error reporting

Salt execution functions routinely raise SaltInvocationError and
CommandExecutionError exceptions. This commit catches them in the jinja
renderer and provides a nicely-formatted error message, preventing the
traceback from being in the render error that is printed to the CLI.
Raise exceptions when trying to read nonexistant files

Prevents a traceback when an invalid timezone is passed
Catch exceptions raised when comparing timezone
Fix lint failure
Update documentation in salt/states/postgres_extension.py
Clarify comments in postgres_extension.py
Added missing whitespaces after comma to prevent lint-errors.
service.available should also use chkconfig, to support xinetd services
Merge pull request #12724 from terminalmage/issue12696

Jinja renderer, timezone module/state fixes
Merge pull request #12711 from eliasp/states_pkg-allow_updates

Allow packages to be updated on their own
Fix timedatectl parsing for newer systemd releases

systemd 210 changed the output for timedatectl, changing 'Timezone' to
'Time zone'. This commit fixes a traceback that occurs in
timezone.get_zone for these newer versions of systemd.

Additionally, for get_zone() and get_hwclock(), parsing of timedatectl
has been changed from an ugly and unwieldy shell one-liner to actual
python logic.

Finally, output_loglevel has been set to 'debug' for all shell commands
in this module, part of a greater effort to make the logs less noisy.
Merge pull request #12715 from jaloren/develop

Fixes 12702: now a traceback exc is written when returner fails
lint per #12715
Merge pull request #12727 from grue/patch-2

Documentation update for salt.states.postgres_extension
Merge pull request #12735 from DoubleNegativeVisualEffects/xinetd-services

service.available should also use chkconfig, to support xinetd services
Merge pull request #12737 from KennethWilke/develop

redis external pillar, more redis exec
Merge pull request #12673 from steverweber/extra_autosign

auto accept keys in minions_autosign