Fix ineffecient queries: OR => IN

This PR fixes the places where multiple ORs are used instead on an IN.
So instead of doing:
```WHERE id = 1 OR id = 3 OR id = 5```
it should be:
```WHERE id IN (1, 3, 5)```

Using IN vs OR:
* Uses less code (as in: query code passed to database object)
* Easier to maintain
* Easier to understand
* And most importantly: IN is 2 - 3 times faster than OR (depending on indexes, how many ORs, etc)

### Testing Instructions
Test the affected components if they still work ok (admin and frontend):
* com_banners
* com_finder
* com_users
* com_weblinks

If possible, also test if there are any negative differences with SQLServer and PostgreSQL.