sql_gen.py: is_temp_col(): Use is_table_col() so that the type of the parameter is also checked

inputs/import.stats.xls: Bolded the ms/row totals. Added note that non-bolded totals are not directly comparable because different methods were run with different numbers of rows.

sql.py: put_table(): Inserting new rows: Removed no longer needed filter-out LEFT JOIN, since the INSERT IGNORE replacement handles duplicate keys

sql.py: put_table(): Inserting new rows: Use insert_select()'s (mk_insert_select()'s) new ignore option to ignore duplicate keys

sql_gen.py: to_name_only_col(): Consider any non-table column, including NamedCol, to be already name-only. This fixes a bug in sql.mk_insert_select() where the value of a NamedCol was removed by to_name_only_col() even though it was needed.

sql.py: mk_insert_select(): INSERT IGNORE: Use an EXCEPTION block for each individual row because "When an error is caught by an EXCEPTION clause, [...] all changes to persistent database state within the block are rolled back." (http://www.postgresql.org/docs/8.3/static/plpgsql-control-structures.html#PLPGSQL-ERROR-TRAPPING). Documented that cursor stays at current position in spite of automatic ROLLBACK on EXCEPTION.

sql.py: mk_insert_select(): INSERT IGNORE: Use RETURN QUERY on the insert query instead of RETURN NEXT on a local var to forward the RETURNING value

sql.py: mk_insert_select(): INSERT IGNORE: Support RETURNING clause. Always return something to set the correct rowcount.

sql_gen.py: Use an as_*() function instead of manually checking the type wherever possible

sql.py: mk_insert_select(): INSERT IGNORE: Added duplicate key handling by using EXCEPTION block to catch unique_violation