[Suggestion] Commodore 64+Amiga System preset

[0x5066]

As the title says, adding a preset to Furnace that has the C64 coupled with the Amiga prepared and ready to go, with channel 3 being omitted. This is in reference to specially crafted SID files that contain a MOD player that uses channel 3 for streamed playback.

[tildearrow]

Dang it! Throwing entire system preset mechanism to the trash...