Command menus now force explicit user input.

Command menus no longer match on display string.

What should 'pyt' match in the following menu?

    Python - doctest (pyd)
    Python - interact (pyi)
    Python - test (pyt)

If the menu allows for matches on the display string then 'pyt' will match
'Python' in the first entry and return 'pyd'.

If the menu does not allow for matches on the display string then 'pyt' will
match the third entry and return 'pyt'. This is clearly what we want.

Calling Menu.make_command_section() now returns a section with
match_on_display_string=False.
Updated TODO.