Add generator CLI to domainmodel and statemachine examples

[spoenemann]

We should add a CLI (similar to #121) to each of the domainmodel and statemachine examples. These should generate code from an input file. The target language is open for discussion.

My proposals:

• domainmodel — generate Java classes with private fields and corresponding getters and setters.
• statemachine — generate C code with a main function that reads from stdin and prints state transitions according to the events entered by the user.

This issue depends on #122: we should finalize the generator API before adding more uses of it.