Add "ledger" command to get ledger information. Make the command

work with no parameters. Fix a bug where the ledger's account/txn
hashes didn't get properly synchronized to the SHA maps. Add function
to get ledger as json object.

RPCServer.h

@@ -42,6 +42,7 @@ class RPCServer  : public boost::enable_shared_from_this<RPCServer>
 	Json::Value doSendTo(Json::Value& params);
 	Json::Value doConnect(Json::Value& params);
 	Json::Value doTx(Json::Value& params);
+	Json::Value doLedger(Json::Value& params);
 
 	// parses a string account name into a uint160
 	// can be local or remote