Add a short description for all known ROMs

[Dirk Hoffmann]

For my web port, I need to display the currently installed ROM in the settings layer. Because the option descriptions are only a few characters wide, I cannot take the ROM descriptions from database. I could work around this by adding some GUI wrapper code, but a cleaner solutions would be to make the core capable of delivering a short description for each known ROM.

[Dirk Hoffmann]

Part of v2.4b1