Support both client and server on same server; set ulimit nofile

Write arbitrary /etc/stunnel/*.pem files via node[:stunnel][:certificates].
Set CAfile and verify options for authentication.
Documented usage of attributes vs. LWRP

Removed recipes/server.rb:
* client_mode is now set per service
* always make a cert;
    it can be disabled with node[:stunnel][:certificate_path] = false