Add 4Play & SNES MAX card support (#946, #972, PR #982)

Support these new cards in slots 3, 4 or 5; based on code from Lukazi.
- extend Configuration's Input prop sheet page.
- add save/load snapshot for both cards.
- add command line switch for alt controller type (for SNES MAX card).
Change to using Registry's 'Configuration\Slot 3' for slot 3 cards (Uthernet, 4Play & SNES MAX).
Update help doc.

source/CardManager.cpp

@@ -33,8 +33,10 @@ Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 #include "Core.h"
 
 #include "Disk.h"
+#include "FourPlay.h"
 #include "MouseInterface.h"
 #include "SerialComms.h"
+#include "SNESMAX.h"
 
 void CardManager::Insert(UINT slot, SS_CARDTYPE type)
 {
@@ -85,6 +87,12 @@ void CardManager::Insert(UINT slot, SS_CARDTYPE type)
 	case CT_Uthernet:
 		m_slot[slot] = new DummyCard(type);
 		break;
+	case CT_FourPlay:
+		m_slot[slot] = new FourPlayCard(slot);
+		break;
+	case CT_SNESMAX:
+		m_slot[slot] = new SNESMAXCard(slot);
+		break;
 
 	case CT_LanguageCard:
 	case CT_Saturn128K: