Graphic improvements

Version 1.3 :
- Adapted the icon to all screen definitions
- Changed compatibility from Android 4.0 Ice Cream Sandwich (API 14)
- Theme set to device default
- Reduced time the splash.png image is shown
- Changed max brush size to 100
- Added Pencil option in the menu
- Resized color picker
- Choose the eraser size when "Erase" is selected
- Changed share message