(Bug 2560) Replace the nouserpic image with a matching padlock on SSL

Icon modified for Dreamwidth by <user name="ninetydegrees">, based on
http://thenounproject.com/noun/lock/#icon-No9489
Merge pull request #363 from afuna/ssl-userpic-bug2560

(Bug 2560) Replace the nouserpic image with a matching padlock on SSL