Improve UX of alpha chooser / initialbar in tablelib and make it responsive

Open up any page which uses the initialbar eg http://moodle.test.local/user/index.php?id=1 , http://moodle.test.local/report/progress/index.php?course=2 , http://moodle.test.local/report/completion/index.php?course=2 etc Do the 'responsive scrub' and make sure it looks decent at all reasonable widths In particular test that in English on a mobile at 320 pixels it wraps into 2 neat lines Rinse and repeat with a few other languages, in particular the ones with extreme word lengths and alphabet sizes, rtl languages, Persian (fa), Khmer (km) and Greenlandic (kl) Repeat all of the above in both clean and boost, and with the boost menu open and closed at various sizes Check if preferences are saved - filter by first/lastname letters, leave the page and return to it - preferences should be saved