[migration] use eschema.type for nicer display when confirmation is asked

[base template header] changeset 6669:e4532c6acf34 introduce a visual regression on standard site, fix it by merging header-left/header-center context, it simplify things and have proper display. Cubes using 'firstcolumn' css class will have to be upgraded

[timetable view] ensure we actually have a user in the rset cell

cleanup