Added usage for nfbitindex
Added command line interface handling code
Read filenames from standard input
Added a source parameter
Moved batch processing code in an individual function
Completed  batch_processing function
Fixed an error handling error in store_bitindex function
Threw out redundant code from batch_processing function
Added additional progress message
Store bitindex only at the end and not after each processed file
Set firstseen and lastseen fields
Updated todo list
Added command line option handling code for querying a file
Added skeleton function for the query mode