ILSGateway product stock migration and first reports

@czue PR contains migration of some small part of stock data from ILSGateway. Some logic is directly moved from ILS.
You should try to avoid immediately iterating over the entirety of your SQL query results, and should try to let Postgres do the work for you.

`alerts.values_list('text')`

The above will return an array of tuples, so might behave like the array of one element arrays you're already returning:
`[(u'1000',), (u'1000',), (u'1001',), (u'1001',), (u'1002',), (u'1002',), (u'1003',)]`

If you pass `flat=True` in (`alerts.values_list('text', flat=True)`), the result is just an array of items, instead of tuples.