registration password validation

[rdallman]

this may be built into HTML and I'm missing something, but check that the password fields match and probably will have to check to see if the email is already in use. In theory, the password could be done with javascript but since we'll have to hit the server to check that the email isn't already in use it could all just be done there. this is loosely tied to flash messages, but if the functionality is there it's easy to translate to flash.

[michellefish]

done