[FIX] web: various fixes in list view navigation

With this commit, we try to improve the way navigation is done in the
list view.  In particular, we want to make sure that pressing TAB on the
last editable cell move the cursor to the next line (and create a new
line if necessary).

Also, we add a few tests for keyboard navigation (it was almost not
tested before this commit, and while working on this commit, it was
broken at some point).