Course re-run section and refs to it in others

@explorerleslie, @talbs please check for accuracy and completeness
@WatsonEmily please circulate to PMs for level of detail, other likely questions to address, format
@mhoeber , @srpearce please consider this a developmental/copy edit
@sarina, @nasthagiri if you have time I value your input also!

The way that you change release dates will look a bit different, yes. That you do need to do this will remain the same. (this change will actually go out AFTER the publishing changes, so there's a bit of rework ahead of me on this)