Expanded EAP methods should get their packets for handling starting at
the op-code field. They're not really interested in
type/vendor-id/vendor-type fields.
Only EAP as the inner authentication option is supported. According to
wikipedia this is the most popular EAP-TTLS use case, with MD5 as the
inner EAP's method.
Add the EAP-TLS authentication method. Currently, all the credentials
data is read from the provisioning file even though things like the
private key passphrase should possibly be obtained from the dbus agent.