added the abstraction of the database cursor for the index search, and added the
function for perform search on data pack index
private api on mongodb and additional fix
- some private api has bee created for mongodb index cursor
- fixe strange behavior on multithreaded usage of index scanner
- changed the index document, now include data pack size and block path.
refactors VFSQuerable file to VFSQuery and added more info to index
QueryManager creation and channel update for a query submission
added a separation form VFSQuery and data block reading management

NOTE: some techniques need to be implemented for let more thread to read at different area of the dab lock without opening the same data block more times
al query part are development  but never tested.
- all sub layer of query engine are development but never tested
- direct io answer to query api has been developed but not tested
finished all query round-trip but crash very badly...need to be tested
first working query