GOS Type 3 implemented

- Python code to generate data for header
- Javascript code to parse this data
- Checked with NotoSansKRThin and cff fonts which are included in the diff
- bitarray library is used in Python
I'm going to start our own cff_lib.py file to allow us to do somethings that TTX/fontTools does not do easily (just a FYI, no change required here).