emails: expose profile link on registation email. Implements #3999.

rhodecode/templates/email_templates/user_registration.mako

@@ -13,9 +13,10 @@ A new user `${user.username}` has registered on ${h.format_date(date)}
 - Username: ${user.username}
 - Full Name: ${user.firstname} ${user.lastname}
 - Email: ${user.email}
+- Profile link: ${h.url('user_profile', username=user.username, qualified=True)}
 </%def>
 
 ## BODY GOES BELOW
 <div style="white-space: pre-wrap">
 ${body_plaintext()}
-</div>
+</div>