class_maker.py should better support new versions of existing algorithms

[Keith Brown]

I've just tired to create a new class file for #9501 using the class_maker.py file, however it didn't run properly as there was already an rst file for version 1 of that algorithm. In the end I had to add the --no-rst flag so i could create the class.

update the script to better support the creation of new versions of existing algorithms

[Stuart Campbell]

This ticket has been transferred to github issue ​10516