Adds a function to store/update dns serial numbers

avoid manually updating the serial number of a
zone file each time the zone file changes.

Example use:

/etc/bind/example.com.zone.include:
  file.managed:
    - source: salt://dns/example.com.zone.include
    - template: jinja
    - user: root
    - group: root
    - mode: 644
    - require:
      - pkg: bind9
    - watch_in:
      - service: bind9

/etc/bind/example.com.zone:
  module.wait:
    - name: dnsutils.serial
    - update: True
    - zone: examplecom
    - watch:
      - file: /etc/bind/example.com.zone.include
  file.managed:
    - source: salt://dns/example.com.zone
    - template: jinja
    - require:
      - module: /etc/bind/example.com.zone

The include file contains all the dynamically generated zone data, the
example.com zone files is mostly static and has a serial number like:

{{ salt['dnsutils.serial']('examplecom') }}      ; serial number YYMMDDNN
remove unwanted import
add keep_symlinks parameter to push
Fix indentation errors and inconsistencies

Documentation for new requirements did not consistently use two spaces for
indentation or even no indentation at all.
Adding the ability to have network.ping return a boolean, True or False, if the ping was successfull or not.  Also adding the ability to specify a response timeout.
Update systemd.py

[Feature]
add the possibility to mask/unmask services with systemctl
Update systemd.py

[Bugfix] fix pep8 issues
Added Pepa v0.6.6, improved error handling and support for getting grains using REST API for validation
Merge pull request #15966 from SvenMW/fix

Fix pep8 issues
Merge pull request #15967 from mickep76/develop

Pepa v0.6.6
Merge pull request #15828 from ptonelli/develop

Adds a function to store/update dns serial numbers
Merge pull request #15938 from babilen/doc/req_indent

Fix indentation errors and inconsistencies
Merge pull request #15947 from garethgreenaway/15880_network_ping_return_boolean

Additions to network.py module
lint for pepa, @mickep76
Updated win_dns_client state, added 'replace' parameter that will remove any DNS servers that are not in our list.  Also added additional change logging to show added, removed, or re-ordered DNS servers
Remove unused function
Merge pull request #15976 from thatch45/pepa_lint

lint for pepa, @mickep76
minor modules.dnsutil._to_seconds() cleanup

rename `time` arg to avoid shadowing imported `time` module
catch more specific exception when doing conversion to int
Merge pull request #15982 from hulu/dnsutil

minor modules.dnsutil._to_seconds() cleanup
fix indentation