webapp

We are deprecating webapp based signup. It leads to an
inconsistent state for mail providers and offers no useful
interactions for vpn providers either.

Instead of trying to deal with the halve way signup through
the webapp we require signup through bitmask app which can
also create the pgp keys for email and download and use the
cert for vpn.

In addition this reduces the attack surface for js injection,
phishing and other browser based attacks.

For now we still keep the signup form in case providers link
to it directly. We also keep all the tests based on it. Cleanup
will happen right after 0.10.0 release.