search should be independent to distro series

[Anthony Lenton]

When searching for an application you're always taken to results for a specific distroseries. Instead you should see results from all distroseries. Each app should be listed only once, but the displayed result should be from the latest distroseries that app was available on.

Steps to reproduce:
 - On natty, go to https://apps.ubuntu.com/
 - Enter some search, eg "ubuntu"
 - You're redirected to https://apps.ubuntu.com/cat/search/natty/?q=ubuntu and 223 results are returned
 - Notice that in the sidebar it offers 'Oneiric' as an option, clicking on that takes you to https://apps.ubuntu.com/cat/search/oneiric/?q=ubuntu with 246 results returned.

Expected result:
 - The first result would take you to a distroseries-agnostic url like https://apps.ubuntu.com/cat/search/?q=ubuntu with all 246 results returned (maybe more if some of the results from natty aren't available on oneiric). It's fine to then be able to restrict the search to oneiric or natty, but it shouldn't "guess" your distroseries immediately when you search.