This is the base class of most Draft Gui Commands,
particularly those which were developed a long time ago.
It is inherited by `Creator` and `Modifier`
to set some specific options for some tools.
Newer Gui Commands do not use these classes and thus
are independent of `DraftTool`.
Nevertheless, in the future we expect to organize further
the commands so that they all derive from a few classes,
so that they all share some common properties and behaviors.
