Find series by stamps catalog number: add support for multiple series

[php-coder]

After fixing #287 I broke finding series by catalog number (#119) in case where more than one series have the same catalog numbers.

Current behavior:

1. find series by catalog number
2. if there is no such series then show 404 error
3. if there one series then we redirect to the page with info about series

We need to modify step 2 and 3 and instead of redirecting, show the page with links to series that were found. Format of these links should the same as on collection info page, for example: Prehistoric animals » Angola » 1994, 5 item(s)

Also on this page we should show message about how many series were found.