Implement window to view data of Visual Novels

[darklinkpower]

Add support to open a window for a game that opens a window to display data available on VNDB, including tags, relations, characters with their information, screenshots, etc. in as similar fashion to what VnManager does.

Some screenshots of that software to see what I mean:

[Mithnar]

Awesome idea, but I'd probably implement it as an independent add-on, this doesn't seem in the scope of a metadata provider.

I won't be working on it until bulk metadata is implemented though.

DIscussion on how this should be implemented is very welcome.