Ahodges/documentation/doc608

@gwprice , @jimabramson , @marcotuts , @lou-wang , @explorerleslie , @WatsonEmily  please check accuracy and completeness (note the files have different audiences, staff vs. students).
@mhoeber @srpearce please copy edit.
@gwprice , @explorerleslie : added based on Leslie's question (in another PR) about the difference in the counts