Added email verification for users

The verification email is sent if needed when profile is updated (either when the email is changed from the previous time or it was an old account and didn't have the token value)

You can test it here: http://verify.gae-init.appspot.com/profile/

![screen shot 2014-08-14 at 19 46 25](https://cloud.githubusercontent.com/assets/125676/3924464/a9cb5d1e-23dd-11e4-9c63-54d00363f42c.png)
I've seen this kind of verification links and I was always annoyed by the fact that they were asking me to login first, or after the verification. This link can be used only once and it automatically logs you in as well.

It looks like it's less secure of course, but on the other hand if someone got access to your email, they can always reset other passwords and do bad things anyway, so it won't solve the problem of a user that left their email unattended.