FAB-1336 Add new ledger blockstorage index.
Add a new ledger blockstorage index for History that will map (blocknum,trannum) to the file storage location for this block transaction This index will be used for the API GetTransactionsForKey() for (chaincode1,key1). It will do a key range query on chaincode1~key1 to pick up all chaincode1~key1 records. Results will indicate the set of (blocknum,trannum) transactions that updated this key. Change-Id: I81da09e5526d7e2966634c78a03d34011d514442 Signed-off-by: Mari Wade <email@example.com>