Adding Swimm.io tutorials

[ShayNehmad]

What is this?

Fixes #764 .

Adding the following Swimms:

• New Configuration value
• Zero Trust test
• PBA
• PBA for MITRE
• PBA with override run
• System Info Collector
• RCE web Exploit
• RCE non-web Exploit

Plus, add the following:

• Swimm docs to docs hub, under "contrib"
• CI validation of Swimm units

Checklist

• Have you added an explanation of what your changes do and why you'd like to include them?
• Have you successfully tested your changes locally?
• Is the TravisCI build passing?

Tests include someone doing all swimms from start to finish and making it through no bugs using the provided documentation only.

Proof that it works

Changes

Are the commit messages enough? If not, elaborate.

[codecov]

Codecov Report

Merging #766 into develop will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff            @@
##           develop     #766   +/-   ##
========================================
  Coverage    60.52%   60.52%           
========================================
  Files          165      165           
  Lines         4948     4948           
========================================
  Hits          2995     2995           
  Misses        1953     1953           

Impacted Files	Coverage Δ
...chema/definitions/system_info_collector_classes.py
.../infection_monkey/system_info/netstat_collector.py
monkey/common/data/__init__.py
monkey/common/network/network_utils.py
monkey/common/data/post_breach_consts.py
monkey/infection_monkey/tunnel.py
...ection_monkey/system_info/system_info_collector.py
...cessing/system_info_collectors/test_environment.py
monkey/common/utils/exceptions.py
...nd/cc/services/telemetry/processing/post_breach.py
... and 320 more

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