Add GK1&2 and Phantasmagoria 1&2

This adds support for:

• Gabriel Knight 1 & 2
• Phantasmagoria 1 & 2

I own these on Steam, and that is the only version I have tested. I suspect this is similar to the GoG version, as the ISO for GK1 is named GK1.GOG.

I also noticed that I messed up the changelog; I was getting warnings because there wasn't a maintainer line. I hope adding one wasn't too presumptuous.