[Feature] Introduce Apache-Airflow for Orchestration

[noelmcloughlin]

Issue/Feature Description:

Document Apache-Airflow Installer for Linux for Orchestration (the installer is available from Saltstack Formulas).

$ curl -LO https://raw.githubusercontent.com/saltstack-formulas/salter/master/go.sh && bash go.sh
$ sudo /usr/local/bin/salter add airflow

Airflow GUI
https://192.168.1.n:8080 user/pass: airflow/airflow)

Other Notes / Environment Information: (Please give the env information, log link or any useful information for this issue)

vagrant@ubuntu1804:~$ sudo /usr/local/bin/salter add airflow
==> This script will add: airflow
press return to continue or control-c to abort
cloning redis-formula from saltstack-formulas ...

cloning postgres-formula from saltstack-formulas ...

cloning airflow-formula from saltstack-formulas ...

local:
    ----------
    base:
        - redis
        - postgres
        - airflow
run salt: this takes a while, please be patient ...
--------------
Succeeded: 101 (changed=75)
Failed:      0
--------------
See full log in [ /tmp/saltstack-formulas-salter/log.202012081106 ]

/////////////////////////////////////////////////////////////////
        airflow for salter has completed
////////////////////////////////////////////////////////////////

[noelmcloughlin]

Apache 2.0 is just released.