Logic to 'rebase' a ledger to a different previous ledger.

This code does not assume the new previous ledger is valid
or trusted.
1) Validate sequence numbers and basic information.
2) Create a new ledger based on the new previous ledger.
3) Compare the old previous ledger and the new previous
ledger.
4) Try to include any missing, valid transactions in
the current ledger.
5) Traverse the old ledger based on the old previous ledger,
try to import any transactions into the new ledger.

SHAMap.cpp

@@ -389,9 +389,6 @@ SHAMapLeafNode::pointer SHAMap::createLeaf(const SHAMapInnerNode& lowestParent,
 	for(int depth=lowestParent.getDepth()+1; depth<SHAMapNode::leafDepth; depth++)
 	{
 		SHAMapInnerNode::pointer newNode(new SHAMapInnerNode(SHAMapNode(depth, id), mSeq));
-#ifdef DEBUG
-		std::cerr << "create node " << newNode->getString() << std::endl;
-#endif
 		mInnerNodeByID[*newNode]=newNode;
 	}
 	SHAMapLeafNode::pointer newLeaf(new SHAMapLeafNode(SHAMapNode(SHAMapNode::leafDepth, id), mSeq));