Cleanup date editor,

Cleanup date editor,

* hildon-widgets/hildon-date-editor.c

        (BUTTON_SPACING): removed. Use HILDON_MARGIN_DEFAULT
        (MAX_DATE_LEN): removed. Specify buffer lenght in code.

        (hildon_date_editor_get_font_width): removed (legacy static
        function), use gtk_entry_set_width_chars instead.

        (hildon_date_editor_mnemonic_activate): removed mnemonic
        activation handler, since it's no more used by HildonCaption.

        - Removed some meaningless code (if (somewidget != NULL)) from
        size allocate.

        - HEAVILY modified key_press, completely removed if/grab_focus
        spaghetti by gtk_widget_child_focus

        - Removed input validation from keypress (that would not work
        anyway, since our input method do not generate presses).  => This
        allows to change default return value to FALSE and remove all cases
        that just returned FALSE for some keys.

        - Merged all *_entry_changed callbacks to use the same
        function. Again using gtk_widget_child_focus, but now with return
        value as well to detect last field.

        - Changed that calendar button is no more implemented through
        changing widget hierarchy (old implementation caused critical
        issues when you used both stylus and hardkeys at the same time to
        popup. => finalize method no longer contained anything => removed

        - Locale type is no longer needed after initial setup.

        - Changed idle_popup to popup_calendar_dialog. Idle was a legacy
        hack from the days of background dimming (it was important to
        process background updates before the dimming was done).

        - Changed the field order/delimeters to be correcly derived form
        the locale.

        - Rewrote validation function, combined it with validation done in
        focus_out (since both are now called at the same time).

        - Changed set_date function to set all components at one go
        without doing any validation there between (before setting each
        component).