- added a new parameter in Preferences to control the number of processes created by the Pool() - more processes better performance but also a lot of memory consumed
- made sure that the display of messages in the Status Bar is done asap
- fixed the issue with factory_defaults being saved every time the app start
- fixed the preferences not being saved to a file when the Save button is pressed in Edit -> Preferences
- fixed and updated the Transform Tools in the Editors
