Update release notes for Operator 0.8

We need to update releaseNotes.md to remove the fixed issues, and add the new known issues.

Eric Schneider to scrub the list of existing issues and move the fixed ones into a new section labeled "Fixed Issues" or something similar.

Operator Dev needs to provide a list of open issues that a.) Have a moderate-to-high likelihood of being encountered by a customer, and/or b.) Are very severe if encountered.