Fixed Layout

Fixes the issues that when page is magnified, swipe gestures are hardly detected. (in none or slide transition)
Fixes the bug that when device is rotated, sometimes wrong page is displayed.
Added new functions
/** for landscape mode, set the image which should be located between two pages */
-(void)setPagesCenterImageName:(UIImage*)pagesCenterImage;
/** set the image which is used for resembling the stack of pages on both side of book. */
-(void)setPagesStackImage:(UIImage*)pagesStackImage;
/** enable/disable navigation area on both sides */
-(void)setNavigationAreaEnabled:(BOOL)enabled;