Add database method

This c++ program is supposed to build a sqlite3 database with a table
FLIGHTINFO containing two columns (ID, ARRDELAY). We use a similar c++
program as our FastSample method, i.e. only insert non-empty, not NA
ArrDelay value into the table. To increase the speed we use batch
processing, i.e. use one sqlite command to insert multiple rows.
However, it seems that sqlite3_exec() function is not working the first
time I get there. Still debugging.