Refactor bindings geerator and add support for extra directories
Couple of small fixes to additional_directories support
First Python example: sine objects
HRTF example for python plus fixes:

- C++ examples build to the right place again.
- Python binding generator knows how to properly handle strings, i.e. don't try to automatically convert them like other Sized instances.
Merge branch 'bindings' into subgraphs
Convert the rest of the 3d api to subgraphs