Implement ECP in Ipsilon

Implement ECP in Ipsilon

* add saml2/SSO/SOAP endpoint.
* add check for lasso version, ECP endpoint only exposed in metadata
  if lasso has full ECP support.
* add SSO_SOAP soap authentication handler (used for ECP).
* add SAML binding to transaction so we can determine if cookies
  and other HTTP concepts are expected. Each handler is responsible
  for setting the binding.
* add some constants needed for ECP

https://fedorahosted.org/ipsilon/ticket/4

Signed-off-by: John Dennis <jdennis@redhat.com>
Reviewed-by: Rob Crittenden <rcritten@redhat.com>