PyObjC metadata generator

This project is fairly rough and mostly targetted at updating the metadata included with PyObjC

NOTE: The repository is pretty much unworkable this point, I'm currently working on what's turning out to be a full rewrite.

Open issues: - I'm working on the merging code - "Compiler" needs to be converted to the new data model - "docgen" is incomplete - add "mypy" command to generate .pyi stub files - add proper unittests - "clang" bindings only have partial typing support

• Remove unnecessary bindings
• Add type annotations

• Test tooling with non-system libraries