Add video picking support

Adds methods for specifying AssetsFilter (photo/video/all) and
AssetGroupTypes. Defaults to original behavior.
Merge branch 'master' of https://github.com/hinathan/WSAssetPickerController
Optimized AssetViewColumn by adding transparent border around each thumbnail.
Replaced video indicator images by cleaner icons.
Added storyboard for iPad.
Extended delegate to allow easy handling of errors. (Access permission issues)
Added localization option for UINavigationController title property.

It can now be set via a property called: "albumTableNavigationItemTitle".
Removed obsolete @synthesize directives.
Fixed tiny formatting issues.
Extended localizability, introduced WSAssetPickerConfig class in order to configure text labels and indicator images. Implemented custom UITableViewCell to present AssetAlbums in a more elegant way.