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 <mariwade@us.ibm.com>