[IMP] web: keyboard navigation in kanban view

    1. Added the ability to navigate within the kanban view using UP,
        DOWN, LEFT and RIGHT keys.
    2. By defaults, the focus should be set on the search input field.
    3. From the search input field, using the DOWN key, the focus goes
        to the first card of the kanban
    4. From the search input field, using TAB key, the focus goes to the
        create button
    5. From the create/import buttons, using TAB or DOWN key goes to the
        first card of the kanban, then UP and DOWN keys moves the focus
        from card to card in the same column or if it is not a grouped
        view from left to right.
    6. In grouped view, LEFT and RIGHT keys moves the focus to the next
        column
    7. When on a card, hitting ENTER opens the view of that card.

Not included in this commit
    1. Memorize the position on the kanban when opening an card, than restoring
        when going back to that kanban