- fix Sector group no-successive issue when saving as nmo
- add nong ventilator adder.
- use copy.copy to write some code to reduce the calling of get/set_raw_vt_mtl()
- keep texture when apply virtools mtl preset.
- 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.
