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

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.

Set better limits to the size taken by all BUTTON_WIDGETs when the panel is wide.
For a wide panel (example vertical panel 100px wide) a widget would, before, take a space of 100x100 (for max hardcoded icon size 48px)
Now if panel width exceeds 50px, the widgets' height stays at 50 and does not grow in height anymore.
Same behaviour applies on wide horizontal panels.
The GTK_ARROW also resizes properly for wide panel on BUTTON_WIDGETs with property "has_arrow"

To make sure we have space left and right inside the button
if applet is build-in-process.

Connect to the "change_size" signal and reload the icon at the correct size

fixes weather-icon problems with some themes