runtests: pass remaining arguments as apps to the runner.

And remove the '-a' option. It was pretty custom, and allowed only
a single application to be passed. Now you can pass multiple apps,
in the same form as for the runner.
Add tests for SSL auth.
SSLCertAuthBackend: make request mandatory.

django.contrib.auth is prepared to call backends which don't have
matching prototype. Therefore, with mandatory 'request' the backend
simply won't be called for non-SSL requests.
Merge pull request #77 from mgorny/more-tests

Tests for SSL auth
Initial SSH server support.
Introduce the concept of auth handlers.

Somehow similar to views. We pass command and its arguments as username,
the thing splits it and looks for handler for the command.
Reset RNG in @postfork.
Support authentication using SSH.