Move /usr/share/appdata to /usr/share/metainfo
Important: Legacy Path
AppStream tools scan the /usr/share/appdata/ path for legacy compatibility as well. It should not be used anymore by new software though, even on older Linux distributions (like RHEL 7 and Ubuntu 16.04 LTS) the metainfo path is well supported. Support for the legacy path will likely be dropped completely with a future AppStream 1.0 release.