data: Rename totem's desktop file

So that its name matches the application-id

https://bugzilla.gnome.org/show_bug.cgi?id=734999
data: Make Totem a D-Bus service

https://bugzilla.gnome.org/show_bug.cgi?id=734999
data: Rename the appdata file after the desktop file name change

Our tooling expects that the names match.