Clear up documentation around plugin installation and datasources

[HVBE]

Description

• Clearing up documentation around datasources and plugin installations (automated or via Env-Var)

Relevant issues/tickets

/closes #155

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist

• This change requires a documentation update
• I have added tests that prove my fix is effective or that my feature works
• I have added a test case that will be used to verify my changes
• Verified independently on a cluster by reviewer

Verification steps

[openshift-ci]

@HubertStefanski: The following tests failed, say /retest to rerun all failed tests:

Test name	Commit	Details	Rerun command
ci/prow/images	203e453	link	/test images
ci/prow/format	203e453	link	/test format
ci/prow/unit	203e453	link	/test unit
ci/prow/e2e	203e453	link	/test e2e

Full PR test history. Your PR dashboard.

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[openshift-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: pb82

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• OWNERS [pb82]

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