* New theming module. Adds bootstrap like themes, based on ttkbootstrap. Initial draft. TODO: improve graphics, draw with pillow if available.
* Modified ApplicationLevelBindManager, methods are now class methods and not static methods.
Added parameter master to the init_mousewheel_binding method.
* Modified UI definition. Added project options section.
Options saved: general options, code generation options, style definition, custom widgets.
* New widgets:
- New Hideable Frame widget.
- New PathChooserButton widget.
- New ColorInput widget.
- New docking widgets: DockFrame, DockWidget, DockPane. In alpha status, although pygubu designer uses them.
- New form widgets in alpha status.
- Expose accordion widget hidden in pygubu code (Maybe it will be useful).
* New emit_close_event for pygubu Dialog
* Grid container options, fixed bug: process "all" index first, so specific row/col props are configured correctly.
* New classmethods in Builder object canbe_parent_of, canbe_child_of.
* Added copy_custom_property function
* Added "public" argument to function register_widget
* Added new method Builder.add_resource_paths(path_list: list)