bring ballance virtools helper used fix_texture (renamed as fix material to correspond with the real object operated by this function) into blender plugin.
- 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.
