More work on ledger sequencing:

Track whether ledger is accepted.
	Assert on modifications to an accepted ledger.
	Save accepted ledgers to DB.
	Load ledger by hash/index.
	Ledger history functions, ledger canonicalization.
	'Push' ledger to history.

LedgerHistory.h

@@ -5,12 +5,11 @@
 
 class LedgerHistory
 {
+	boost::recursive_mutex mLock;
+
 	std::map<uint32, Ledger::pointer> mLedgersByIndex;
 	std::map<uint256, Ledger::pointer> mLedgersByHash;
 
-	bool loadClosedLedger(uint32 index);
-	bool loadLedger(const uint256& hash);
-
 public:
 	LedgerHistory() { ; }
 	
@@ -19,6 +18,7 @@ public:
 
 	Ledger::pointer getLedgerBySeq(uint32 index);
 	Ledger::pointer getLedgerByHash(const uint256& hash);
+	Ledger::pointer canonicalizeLedger(Ledger::pointer, bool cache);
 };
 
 #endif