Document certs

[lukehinds]

We generate a lot of certificates. We should document what they all do:

ls /var/lib/keylime/ca/
cacert.crt
cacrl.der
cacrl.pem
ca-public.pem
D432FBB3-D2F1-4A97-9EF7-75BD81C00000-cert.crt
D432FBB3-D2F1-4A97-9EF7-75BD81C00000-pkg.zip
D432FBB3-D2F1-4A97-9EF7-75BD81C00000-private.pem
D432FBB3-D2F1-4A97-9EF7-75BD81C00000-public.pem
private.yml
RevocationNotifier-cert.crt
RevocationNotifier-pkg.zip
RevocationNotifier-private.pem
RevocationNotifier-public.pem

ls /var/lib/keylime/cv_ca 
cacert.crt          client-public.pem
cacrl.der           localhost.localdomain-cert.crt
cacrl.pem           localhost.localdomain-private.pem
ca-public.pem       localhost.localdomain-public.pem
client-cert.crt     private.yml
client-private.pem

ls /var/lib/keylime/secure/        
derived_tci_key  tci_rsa_key  tmpbuenv0_k  unzipped

ls /var/lib/keylime/secure/unzipped 
cacert.crt
cacrl.der
cacrl.pem
D432FBB3-D2F1-4A97-9EF7-75BD81C00000-cert.crt
D432FBB3-D2F1-4A97-9EF7-75BD81C00000-private.pem
D432FBB3-D2F1-4A97-9EF7-75BD81C00000-public.pem