Sorts reverse reference and contribution lists by date, notably using the intrinsically provided dates provided through withResolvedContribs (etc).

Lists are only sorted by the literal property date on the referencing things; additionally disambiguating sorting should be performed before or after. (Although for "before" - the sorting should be done to the array shared by all things, or else the caching is defeated. We declare sorting through YAML loading specs' sort step. Detailed discussion: #code-quarantine)

Re: #383, sorting occurs for every reverse reference list (of the respective input('data') and input('list') all at once, at the same time as the reverse lists / cache records are basically prepared (i.e. on the first call with those inputs). Although we haven't 100% confirmed this is never significantly consequential, some initial measures suggest we'd have to be dealing with pretty big data to run into trouble. (Intro: #code-quarantine, summary: #code-quarantine)

Resolves #529, fixing cover artwork chronology links (whose dates can vary from the respective track). We haven't integrated a predictable sort order into general content yet, and there probably needs to be a broader look at how sorted lists are represented to enable that (e.g. we should only sort according to language rules within ranges that are otherwise ambiguous).