The post list widget created in needs to be generalized, as discussed in a comment there.
Create a "directory" widget for a generalized listing of child artifacts. For this initial ticket, it will rely heavily on defaults, assisted by an "archetype" indication. This initial version will not implement any sort of expression language.
The widget will be named mummy:directory.
By default, it will simply list the navigable child artifacts in a <ul> structure, sorting in ascending order by publication date, then in ascending order by title. (A future ticket will allow a sort-by attribute or similar to change this.)
It will use an optional group-by attribute, initially supporting either publication-date or publication-year. (Perhaps in the future an expression equivalent would be it.publishedOn.date? Even with an expression language, some fields might be difficult to access with expressions; what if we wanted to support both publishedOn and publishedAt? We may have no choice but to always support some keywords such as publicationDate.) Each value will support an optional preceding + or - to indicate ascending or descending order, respectively, e.g. -publication-year for reverse order by the year of the publication date.
It will use an optional archetype attribute, initially supporting a single value: blog. If this is present, no group-by attribute will be allowed (at least for this ticket) and behavior will be equivalent to that developed in (with improvements as necessary). Specifically it will handle sorting like GUISE-109: in reverse order by publication date, then in ascending order by title.