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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