Fine tune config (rebased onto develop)


This is the same as gh-893 but rebased onto develop.

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In an effort to make the `Ice.IPv6` troubleshooting info clearer (based on https://www.openmicroscopy.org/community/viewtopic.php?f=5&t=7456&start=20) the post-install sections have been slightly revamped, reordered, and cleaned up.