Version 0.75 :

- lots of small fixes…
- change in the prefs file
- clean parts of code ( update, prefs file )
- add a Preference window ( define update at launch or not, and test for update )
- change in the Circle window ( had a poor rendering on Windows )
- re-organisation of some menus,
- add an error module to catch little nasty bugs
- improve custom tunings window
- last tuning used will saved