Allow disabling redirecting when using old product or category URL

It is hard to re-use the category view or product view when there's more
than one valid URL per product/category. E.g. for my site, categories
are accessible under /<brand>/<model>/<category>/.

A global setting wasn't introduced because I assume that when one
requires trickery as above, it's likely that the view has to overridden
anyway.