Add Virtual Pinball Spreadsheet id to game metadata, dialog

[Billiam]

This is primarily to support user scripts that want to work with virtual pinball spreadsheet, either for score tracking or to find table media.

While this can be added directly to the database XML currently, user scripts must then parse the XML file directly instead of reading the info from the game object. (ex: https://github.com/timhobbs/PinballY-Scripts#vpc-high-score-corner)