Fix #922: Bindings generator generates .pyc files
auto merge of #1735 : tgkokk/servo/python-write-bytecode, r=kmcallister

Forgot to actually claim #922. I hope no one is working on it.

I removed `PYTHONDONTWRITEBYTECODE=1` from every relevant file and I added code for removing `*.pyc` files in `clean-script` in `mk/clean.mk`. You might want to move the main logic into a function like `REMOVE_PYC_FILES`, since the files will exist eventually in other trees under `/src`. I used `find` in order to find all `*.pyc` files, since they might be in other subdirectories.

This is my first PR, so feel free to give me any feedback you might think is necessary.
Implement JSManaged for DOM objects.
auto merge of #1591 : jdm/servo/jsmanaged, r=Ms2ger
Remove methods from IDL that don't do anything useful.
Move HTMLDocument members to Document.
Remove HTMLDocument.
Remove document::DocumentType (fixes #1730).
Remove DocumentTypeId.