Performed cartesian join of column info in Perl instead of Oracle.

Oracle's ALL_CONSTRAINTS and ALL_CONS_COLUMNS tables are not indexed or
optimized for query.  DBD::Oracle's foreign_key_info can take anywhere between
4 to 18 seconds to get information for a single table, which is dreadfully
unacceptable when one has a database with almost 1000 tables.  This new
algorithm sacrifices some client memory in exchange for an 11x speedup.