elasticsearch returner.

Dependencies:

- official elasticsearch python client
- jsonpickler.

configuration is defined in the master config file:

```yaml
ext_job_cahe: elasticsearch

elasticsearch:
    host: 'some.host.com:9200'
    index: 'salt'
    number_of_shards: 1 (optional)
    number_of_replicas: 3 (optional)
```
Added preliminary documentation
correct master settings
add link to elasticsearch client library docs
fixed lint errors
Added module and state for adding new firewall rules
Add extra handling to highstate outputter for 'Comment'
Ensure that freebsd service rc.conf ends in newline before appending
Added a _utils sync mechanism for distributing utility source files to minions (#12712)
Fixed whitespaces
Fixed incorrect indentation
Better sysctl test detection.

Closes #12408
Pylint
Populate 'Changes' on docker.installed container creation
Move mine_interval example to a minion conf file

mine_interval has no effect when added in a pillar
Change default output_loglevel to debug
Remove output_loglevel='debug'

With the default loglevel now set to debug, setting it to debug when
invoking cmd.* is redundant.
Fixed rST syntax that was causing the PDF not to build
Merge pull request #12863 from whiteinge/doc-rst-latex-fixes

Fixed rST syntax that was causing the PDF not to build
Added note when using the loader to run modules that contact the master

Closes #12732