Allow args in __init__; and use them to call make_id.  So the user doesn't have to call anything but __init__.
Minimally use the new basic_id class.
The plotspec class's _id, used in two print statements, is now named _strid.
The plotspec class's _id is now named _strid.
BTW, this file hasn't been used for anything for months, and maybe should be deleted.