Don't keep filters when clicking on context rows.

There could be no matches for units from context rows while keeping the
filtering criterion, leading to queries with no results and unexpected
behavior.
Plain ol' js just works fine (and it's more performant).
Remove title from navigation buttons in case they are disabled.

Avoids inconsistent tooltips.
Filter submissions made from the web interface.

Unless this filtering criterion is applied, there were occasions were
languages and translation projects were displayed with all the numbers in
the row being zero.
Don't display zero in contribution tables.

Also simplified the returned data structure.