history: add a module for analyzing git history
history: add sub that returns date added for every song in history
klomp-update: generate datecache file on update
klomp: add reverse arg to sort orders
klomp: read date-cache and set dateAdded on all songs returned by queries
klomp: add date-added sort fct
klomp: build various-artists regex up front
klomp: add date-added filter with syntax @@d### for showing the latest ### songs