Originally, GBindingGroup started with Builder as a way to simplify all
of the third-degree object bindings necessary around Model-Controller
objects such as TextBuffer/TextView.
Over time, it has grown to be useful in a number of scenarios outside
of Builder and has been copied into a number of projects such as GNOME
Text Editor, GtkSourceView, libdazzle, and more.
It makes sense at this point to unify on a single implementation and
include that upstream in GObject directly alongside GBinding.
