commtrack registration flow (Case:52839)

adds an unexposed register/commtrack page which leads to a new commtrack
domain page.  This is done with hidden fields and by adding a
domain_type component to the url.  Could be easily hooked into a
canonical list of domain types.
merge master
fix resend confirmation url
merge master
remove dead function parameter
change user registration url
Merge pull request #643 from dimagi/commtrack-registration

commtrack registration flow (Case:52839)