A tree-like data structure that can be used with the GtkTreeView.
The GtkTreeStore object is a list model
for use with a GtkTreeView widget. It implements
the GtkTreeModel interface, and consequentialy, can
use all of the methods available there. It also implements the
GtkTreeSortable interface so it can be sorted by
the view. Finally, it also implements the tree drag and drop interfaces.
Create a new tree store with a number of columns.