Add last seen and post count to user card

[codinghorror (Jeff Atwood)]

@sam

Post count is ubiquitous on all forum software, usually way more prominent than the user card. Adding it makes stuff less surprising for users that came from that world.

I can only support making the user card an editable template, where they can put whatever fields they want from the user profile there. I do not support making post count part of something we ship as default.