Note that GTK+ sets a default title of _("About %s") on the dialog
window (where %s is replaced by the name of the application, but
in order to ensure proper translation of the title, applications
should set the title property explicitly when constructing a
GtkAboutDialog

https://developer.gnome.org/gtk3/stable/GtkAboutDialog.html

*clear applet gsettings on dispose to stop crash and memory leak introduced in github.com/mate-desktop/mate-panel/commit/10b9c30fc79de5f8d9516ba153df233c4968da65

*tray: fix misplaced g_return_if_fail check

Note that vertical and horizontal panels require different options in the grid, as "homogenous" is needed in rows for horizontal panels and columns in vertical panels to prevent icon rendering problems including icons growing without limit when the tray is moved from a horizontal to a vertical panel

The only option in the preferences is a GtkSpinButton
for the user to be able to set the icon sizes easily
without having to use dconf-editor.

The new GSettings allow to change and remember the minimum icon size for the grid.
The default icon size is set at 24px.

New grid sorting/display functions to arrange notification area icons in a self reorganising grid
main changes in: item_added_cb(), notification_notify() -> refresh_notify().
update_size_and_orientation() is no longer needed
the grid auto arranges on any size-allocation which includes orientation changes.
Grid is now refreshed with refresh_grid()/determine_grid_properties()/reorder_items_with_data().
based on the min_icon_size property
the main applets' code can call na_grid_set_min_icon_size() to update the grid icon size.

box/Box/BOX changed to grid/Grid/GRID as a preliminary step
to prepare for changing GtkBox in na-box/na-grid to a GtkGrid
to make the notification area work well on vertical and wide panels
note: even if everything is renamed to grid, the GtkWidget is still a GtkBox
thats why GtkBox and GTK_TYPE_BOX have not been renamed.