Disabled servers (closes #83)

Signed-off-by: Daniele Ricci <daniele.athome@gmail.com>
Direct SSL (via X.509 bridge certificate) endpoint (#91)

Signed-off-by: Daniele Ricci <daniele.athome@gmail.com>
Key renewal: use given key directly if signature is valid

Signed-off-by: Daniele Ricci <daniele.athome@gmail.com>
Fix send error stanzas during key registration

Signed-off-by: Daniele Ricci <daniele.athome@gmail.com>
Exclude disabled servers from hostlist

Signed-off-by: Daniele Ricci <daniele.athome@gmail.com>