create_exercise: Remove logic that adds version parameter and Generate exercises on a per test-case basis

[With problem-specifications removal of the version property from canonical-data.json](https://github.com/exercism/problem-specifications/pull/1678) and the [reorganization of problem-specifications](https://github.com/exercism/problem-specifications/issues/1674), our exercise generator is out of date.

Read the reorg link for details, but basically when we generate exercises from problem-specifications we need to use the `.meta/tests.toml` files created in #262 for each exercise. The tests.toml files will tell create_exercise which test cases to generate. And that is a big change.

So the create_exercise will need to be updated to do the following:
- [ ] Determine if the exercise already exists by checking whether the exercise folder exists and contains a `.meta/tests.toml` file.
- [ ] If the exercise does already exist, then create_exercise will only check to see if the `.meta/tests.toml` is still up to date. You may use the new canonical_data_syncer tool (via /bin/fetch-canonical_data_syncer) to do this check. Just need to verify that it fails properly.
- [ ] If the exercise is missing the `.meta/tests.toml` file, then throw an error describing that the toml file is missing.
- [ ] If the exercise does not exist or , then create the exercise as normal, but only the test cases defined in the `.meta/tests.toml` file.