sql.py: put_table(): Moved post-insert code outside while loop because it will now always be run (there are no longer special cases where the postprocessing doesn't happen)

sql.py: put_table(): Missing mapping for NOT NULL column: Just create an empty pkeys table, since the missing rows' pkeys will be set to NULL later

sql.py: put_table(): Joining together output and input pkeys: Use new sql_gen.join_same_not_null

sql.py: put_table(): Setting missing rows' pkeys to NULL: Use new sql_gen.join_same_not_null

sql_gen.py: Join: Added join_same_not_null. to_str(): Refactored to switch order of left and right tables and cols because left_table is on the right in the comparison, and using the sides of the comparison instead of the sides of the join makes the code clearer.

sql_gen.py: Renamed join_using to join_same to reflect that it can also be used without USING

sql.py: put_table(): Set missing rows' pkeys to NULL

sql.py: put_table(): NullValueException: no mapping for missing col: Fixed bug where run_query_into_pkeys() was still using insert_joins instead of input_joins

sql_gen.py: Added MockDb. All str() methods: Use self.to_str() with mockDb.

sql_gen.py: Use db.esc_name() instead of sql.esc_name(db, ...) so passed-in db can be a mock object