Add support for listing folders and their content
In order to implement paging for videos on vlc-android, we need a way to replicate the grouping feature.
This can be achieved by allowing users to list their folders (which is often the same result as grouping video by filename, for camera/application media).
A way of listing all known folders
IMediaLibrary::folderswith the usual filter/sort feature
- Most likely a shortcut to know if a folder contains any media or not, to filter out folders with no media
A new member function in the IFolder interface to list media contained in a folder
- The usual sorting & filtering parameters must be handled
- Media can be filtered out by their types