Pygubu

* Improved ui tester.
* Fixed issues 54, 58, 59, 60

* Allow to specify variable names when importing tk variables.
* Allow to register an already created tk image.
* Allow to specify loggin level from console command.
* Added new pathchooser input widget.
* Improved README (thanks to Nelson Brochado)
* Fixed issue 52

* Added custom widgets preference option.
* Added appdirs dependency.
* New sticky property editor.
* Fixed issues 40, 45

* Fixed issues 39, 41

* Remove old pygubu.py script for old installations.
Create pybugu-designer.bat file for windows platform. Fixes 38

* Fixed bug: color value setting to None when presing Cancel on color selector.
* Add '.png' format to Stockimage if tk version support it. fixes 36
* Minor changes to main UI.