Check for controller compatibility and warn if incompatible settings are used

The disc header contains information about compatible peripherals. It's a simple list of characters with specific meanings:

• A = Analog controller (includes 3D Control Pad, Virtua Stick)
• C = Link Cable (Japan)
• D = Link Cable (USA)
• E = 3D Control Pad
• F = Floppy Disk Drive
• G = Virtua Gun
• J = Standard Pad
• K = Keyboard
• M = Shuttle Mouse
• P = Video CD Card
• Q = Pachinko controller
• R = ROM cart (unspecified)
• S = Arcade Racer
• T = Multitap
• W = RAM carts (size not specified)
• X = X-Band/Netlink modem

Game disc headers tend to be honest about these, so it's probably safe to trust this information We'll need an internal database to detect and warn users of incompatible settings and/or force certain configurations to make things work, such as forcing digital mode in the 3D Control Pad for games that don't support its analog mode (i.e. anything without A or E).