Allow users to receive multiple recommendations to one e-mail address

```
An interface to let a user "claim" and merge multiple email addresses.

This isn't as important for receivers of feedme google reader, but for
things like the embedded interface (CHI 2010 recommender), we display what
items where recommended to you, so it's good to merge e-mail addresses.
```

Original issue reported on code.google.com by `marcua@gmail.com` on 20 Apr 2010 at 1:56
