* Fix incorrect save dir path handling for ML format.
Save dir path was split by incorrect os.dependent separator '/'
which was the cause of labels being saved to parent folder.
* Implement path normalization for command arguments.
Renamed 'predefined_classes_file' parameter to 'class_file'.
* rename local variables in main file
* additional renaming of functions and variables
* Rename main file functions
* Rename functions and variables in canvas.py
* Rename functions and locals for remaining files
* Rename non-Qt derived class' members
* Rename members of Qt-derived classes
* Fix paint label issue
* adds createMl reader & writer class
* adds getFormatMeta function to support more than two save_format
* adds CreateML read & write support
* adds format CreateML icon
* fixes negative height/width
* removes type hints
* fixes coordinate calculation
* adds unit test
* removes typehint
