Build the LedgerEngine logic into the Ledger class.

Add index rules for account state and ripple nodes.

src/LedgerIndex.cpp

@@ -0,0 +1,14 @@
+
+#include "Ledger.h"
+
+uint256 Ledger::getAccountRootIndex(const uint160& accountID)
+{ // Index is accountID extended to 256 bits
+	return accountID.to256();
+}
+
+uint256 Ledger::getRippleIndex(const uint160& accountID, const uint160& extendTo, const uint160& currency)
+{ // Index is 160-bit account credit extended to, 96-bit XOR of extending account and currency
+	uint256 base=getAccountRootIndex(extendTo);
+	memcpy(base.begin() + (160/8), (accountID^currency).begin(), (256/8)-(160/8));
+	return base;
+}