This effectively unifies the InfoWrapper and detect_file_format() behavior into a single approach that can work stream-based or with a file on disk. Note that the wrapper name is also changed as "InfoWrapper" was named for glance's intended use-case, which was metadata extraction. Since this has obviously grown in scope, now is the time to change that name. Change-Id: Id61f7472f791fc258ec7d0238568c379a7b27823