Support sub-resources in discovery API generation

[dgresham]

This prefixes resource names with the name of their parent resource, which can lead to some unwieldy Resource and Request class names; it's an easier way to disambiguate than splitting into more libraries still (which would be a substantial refactor, I believe).

emitter_test.dart doesn't seem to be run by the presubmit script, and I haven't yet got it to run myself, but I believe it should work (I've tested the apigen binary manually, and it looks correct).

[yjbanov]

Our tests for the code generator, which includes the emitter, are end-to-end, testing the output of the generator given sample input. These tests are under test/generated. To add a test, create 3 files:

PREFIX_test.dart - the actual unit test code
PREFIX_test.json - sample input discovery schema for the generator
PREFIX_test.streamy.yaml - configuration for the generator

Streamy's pub transformer will automatically pick up the new files and run them through the generator, making the output available to the test.

Add the new test to test/all_tests.dart. Finally, to run tests:

$ pub serve
# Then in another terminal window
$ dart -c --package-root=http://localhost:8081/packages http://localhost:8081/all_tests.dart

BTW, heads up, we're going to be promoting master-v0.2 to master today or tomorrow after #233 is in, so you might need to rebase and create a new PR (unfortunately Github doesn't support changing target branch for existing PR).

[dgresham]

OK - I can do that, no problem. Have added tests (and they uncovered a bug, yay!). Will keep an eye out for the branch change and re-send.

[yjbanov]

master-v0.2 branch is now master. Please resend your PR onto master (also, fetch and rebase; a small fix in the emitter went in recently). Looked briefly at the code changes. They look great so far. Will dive a little deeper tomorrow.

[dgresham]

Done - #237