Add test generator

[cmccandless]

The purpose of this test generator is to create a starting point for contributors when implementing/updating test cases for an exercise. Most likely, all but the simplest exercises will require at least a few minor changes to the generated code, but using a generator will save time for reviewers by creating some consistency between exercises and save time for contributors by reducing the amount of code they must write from scratch.

Other features that could also be added to this generator:

• Generate README using configlet for new exercises
• Generate solution template for new exercises
• Copy solution template to example.py for new exercises (contributor must still implement actual example solution)
• Update config.json with entry for new exercises

[cmccandless]

Once exercism/problem-specifications#996 has been fully implemented, this script can be greatly improved, so let's put a pin in it for now.

[cmccandless]

Updated to detect new schema.

[cmccandless]

Closing, as discussion in #1513 has led in a different direction.