doc updates, normalize roundup => Roundup, add links, typo fixes In Tracker in a Nutshell section Document interfaces.py in table Add links for auditors/reactors to detectors section in table Add links for actions in table Also mark optional components Change roundup to canonical Roundup. Fix unordered lists that were indented causing a list inside a blockquote. UL lists are not unindented. Move internal hyperlink references above the section heading they refer to. Links were jumping after the heading which disorients the user. Change reference to never deleting 'users' class to be 'user' class. fix typos Remove uneeded trailing whitespace.