Add a script for [re]generating test PKI creds

[ghudson@mit.edu: reformatted to limit lines to 79 columns]
Add various client-authenticating PKINIT tests

Add tests for non-anonymous PKINIT:
* FILE: with no password
* FILE: with a password
* DIR: with no password
* DIR: with a password
* PKCS12: with no password
* PKCS12: with a password
* PKCS11: with a password, if soft-pkcs11.so is found via ctypes

[ghudson@mit.edu: reformatted to 79 columns; removed intermediate
success() calls]