Move media related classes and interfaces from AttachmentModule into dedicated MediaModule
While working on #1846 (closed) the idea came up to further refactor the attachment package and module by creating a dedicated media or image module that would be a new home for the various classes and interfaces dealing with images that might deserve their own package now that they are also being used for other purposes. We decided to handle that further refactoring separately to not interfere too much with the ongoing work on #214 (closed)