Added tls cert generation scripts

Change-Id: Iee7c5c6e7a4ce160b688affa584a252781c4cfcc
Add configuration of TLS user certificates

* Added config file options to control certificate user auth and the CA
  certificate file
* Updated the config file schema
* If cert auth is enabled, configure the tls socket accordingly
* Does NOT yet use the certs to authenticate the user session. It still
  uses the previously existing password or PAM.

Change-Id: I80cfe7b66abddeec28fb1849cf684e6a868ca677
Hooked up TLS user certs to authentication system

Implemented a basic authenticator plugin for TLS cert-based user auth.
Still takes the normal username/password message but ignores the contents
entirely. The authenticator returns the cert's CN as the username.

Change-Id: I19b2e986090ca27d9f06e661fa407d162e26aa2a
Finished client certificate authentication

Updated generate script to create the correct key and certificate
files. Added private key passphrase to config, schema, and proxy.
Fixed and tested connectivity with a client certificate. An
unrecognized certificate now causes an AUTH_FAIL to be send to the
client. Updated the README to reflect changes.

Change-Id: I9e9a1a6360b9d7799a66ebcb3cd8e0ff38942b29