Add "Release Date" field to Playlists.

[Odin Valhalla]

Some platforms in my collection, specifically Arcade ones are based on my MAME / Arcade collection, such as CPS1, CPS2, CPS3, Namco System 11, Namco System 22, Cave etc. Would be nice to add the release date / year to these, so it has a cleaner and nicer look in BigBox when year of release is displayed (Colorful theme).