Small dsafilter update. The script now checks the GPG signature of a DSA is valid, and errors out if it is not.

My next focus is making sure what I have here is secure (there's two shell-outs at the moment which I would like to ensure can't be abused). After that, I will probably have a go at re-engineering the script to support multiple package lists, although allowing the behaviour to be tweaked a bit is also on the agenda.

Soon, I expect I'll start using it :-)