Requiring email address at signup

[Matthew P. Schmidt]

Hi everyone.  These days, having an email address is mandatory for most 
types of services.  At JRoller, we had to hack the 
UserNewAction.validate method to throw an error if the username is 
already in use or the email address is missing.  I would like to propose 
that we add these two validation requirements to the core.  Any 
objections?  If not, I can send the patch.

-Matt