OpenID improvements and one other

I could not reproduce failures with any of my OpenIDs on my local box.  I'm a bit suprised that there isn't a DataMapper or similar store, though, I may write one.  That said, I used to use file-based stores without trouble (except on on host, where the tmp folder was just super slow).

This pull request contains some improvements to the OpenID handling in general, as well as some logic to reduce duplicate fetches in the detection.