- try setting center alignment for add floor popup operator. it is not center alignment now because blender's impl but it is better than previous layout.
- add some components icon for more directly visual.
- correct all icon usage. use 'CANCEL' instead of 'ERROR' to indicate error correctly. and move these icon const into UTILS_icons_manager.py
- auto rename generated rail section to match the default name standard.
- give more clear signal about import and export bm file by using Operator.report() function.
- change bl_options and rewrite invoke and draw functions to let floor creating window become more visual. credit: BLumia.
- also change 3ds max align and flatten uv presentation after changing creating floor window.
- seperate icon loader/unload module.
