- fix all `def poll(self)` to `def poll(cls)` to let it fit class method name convention.
- fix wrong progress counter when importing virtools file.
- add light support when importing virtools file.
- add corresponding conflict strategy and resolver for light.
- now grouping, ungrouping clear groups operators will show a report at the bottom of blender to indicate their work have done.
- disable fix material, 3ds max align, select by virtools group operators in edit mode to prevent any possible undefined behavior.
- 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.
