Rosetta Imports page is not able to handle lot of entries

Now that we are importing Dapper into Rosetta, the amount of files pending to be imported into Rosetta is so high that the page at https://launchpad.net/rosetta/imports gives timeouts.

We should figure a way to improve that situation.

The first thing I can think on is to show by default a list of sourcepackages/products that have any file pending to be imported, select it and then, show all the information for that sourcepackage/product and only for them.

Other grouping we could do is based on the importer of those files. In fact, I think we could put there an overview with links to /people/$name/+translations/+pending-imports and /distros/ubuntu/dapper/+source/$sourcepackagename/+pending -imports