after calling this method, you have to call save() on the GridFSInputFile file
on that, you can call setFilename, setContentType and control meta data by modifying the
result of getMetaData
Returns an object containing basic information about the
exectution of the query that created this cursor
This creates a DBObject with the key/value pairs:
"cursor" : cursor type
"nScanned" : number of records examined by the database for this query
"n" : the number of records that the database returned
"millis" : how long it took the database to execute the query
callback to determine if an object is ok to be added back to the pool or used
will be called when something is put back into the queue and when it comes out
multiplier for connectionsPerHost for # of threads that can block
if connectionsPerHost is 10, and threadsAllowedToBlockForConnectionMultiplier is 5,
then 50 threads can block
more than that and an exception will be throw