stock_reports should drop view instead of replacing it

stock_reports.py creates a view but uses "CREATE OR REPLACE VIEW" syntax instead of "DROP VIEW" and "CREATE VIEW" in two separate commands. This becomes a problem if you need to alter the view in another module to add new columns. In the new module you will use "DROP + CREATE",but if you happen to need to update all modules (-u all), executing "CREATE OR REPLACE VIEW" of 'stock' module will crash because in PostgreSQL the REPLACE part is not able to modify the number of columns of a view.

The attached patch fixes this problem.