Issue #2326895 by tim.plunkett: Convert toolbar_element_info() to Element classes.
Issue #2244555 by benjy, ultimike, mikeryan: Use copy() directly instead of file_unmanaged_copy().
Issue #2325477 by tim.plunkett, almaudoh: Convert contextual_element_info() into Element classes.
Issue #2325485 by tim.plunkett, almaudoh: Convert field_ui_element_info() to Element classes.
Issue #2268897 by benny, Berdir, chx: Write per user contact settings D6=>D8 migration.
Issue #2326885 by tim.plunkett, sidharthap: Convert language_element_info() to Element classes.