Some changes for real scrolling to initialIndex and using several galleries

[Bogdan-Stasjuk]

When we using list of galleries it is handy to have public link on UIPhotoGalleryView's instance for identify concrete gallery in UIPhotoGalleryDataSource methods.

For real scrolling to initialIndex in UIPhotoGalleryViewController I added call of setInitialIndex:animated: from viewDidAppear:.

After poping UIPhotoGalleryViewController's instance I see previous image from vPhotoGallery above current viewController about a second in case of images count is more than 1 and current index is more than 0. To solve this issue I added "self.vPhotoGallery.hidden = YES" in "viewWillDisappear:".