Issue #2714529 by benjifisher, mikeryan, dww, iMiksu, heddn, alisonjo2786, alexpott: Add source and destination IDs to the data returned by getMessageIterator()

Issue #2907654 by joelpittet, amateescu, Patrick R., mikran, alisonjo2786: Orphaned menu routes breaking site installs and module uninstalls

Issue #2395853 by LewisNyman, Manjit.Singh, nlisgo, pjbaert, Branislav Bujisic, pguillard, gavin.hughes, onelittlebecca, alisonjo2786, camoa, DickJohnson, manmohandream, davidhernandez, kgoel: Split system.module.css and system.theme.css files into SMACSS style components