GitLab

Also:
* Quick refactor of jinja2 context creation into a builder.
* Switched Attribute/Method to dicts.
* Added a bit more meat more to header template.
* Added nicer parameter handling to run-bindings-tests
* Added stub helper for unit tests.

BUG=654129
R=bashi,yukishiino,haraken

Review-Url: https://codereview.chromium.org/2568693002
Cr-Commit-Position: refs/heads/master@{#437989}