Add user name to Flickr photos page title

I'd like to have the user's name added to the page title on the flickr/%user page, so I've created a patch that adds a callback on the title argument.

I've also added in an extra permissions check on the Flickr ID element of the user form - I don't want all users to be able to have Flickr accounts, just those with the 'view own flickr photos' permission.