- finish uv section of doc.
- fix issue about the wrong calc of coordinate system axis vector in flatten uv (change it from left hand to right hand).
- fix rail uv display text.
- sync PyBMap work. use different library name in different OS.
- add BMap encoding default value according to different OS (Windows and non-Windows) because non-Windows OS, we use libiconv as encoding converter.
- move all pointer properties to a single module and give corresponding visitor.
- add shared importer exporter parameters module thus bmfile import/export also can ref it.
