This class defines the `command_name` of the command,
so that it is output to the report view, and is also recorded
in the log file.
It also stores the current document so it can be used inside the
command.
The class implements with `IsActive` method so that the command
is only active when an active document exists.
Also `GuiCommandNeedsSelection`, which subclasses the former
class. It reimplements `IsActive` in order to be available
only when there is a selection.
Small spacing fixes like imports in separate lines
for more clarity, the module docstring,
and the position of the license.
Remove unused imports. And use proper `ToDo` class
instead of importing `DraftGui`.
