Added details on configuring stage/step status rule

[JimHagan]

This PR adds important on:

• how to interpret the status of stages and steps
• how to use the new configuration UI to change the rules by which status are computed

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2 out of 3 committers have signed the CLA.

:white_check_mark: aso1124
:white_check_mark: JimHagan
:x: nbaenam

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[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you all sign our Contributor License Agreement before we can accept your contribution.
1 out of 2 committers have signed the CLA.

:white_check_mark: JimHagan
:x: aso1124
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[JimHagan]

@nbaenam It looks like you haven't signed the CA for this repo? Please merge when ready.