Allow SP registration from ipsilon-client-install

Allow SP registration from ipsilon-client-install

This optionally allows a SAML SP to be registered with the IDP when
running ipsilon-client-install.  To register an SP, the following
options are used:

  --saml-idp-url   (Ipsilon IDP URL)
  --saml-sp-name   (Name to register the SP as)
  --admin-user     (Ipsilon admin user)
  --admin-password (Ipsilon admin password file)

If the --saml-idp-url option is set, we attempt to register the SP.
The --saml-sp-name option is required if you are registering a SP.
The --admin-user already defaults to admin, so it only needs to be
specified if your admin user has a different username.  If the
--admin-password option is not specified, we prompt for the password.

The --saml-idp-metadata was previously required, but this option is
redundant if the new --saml-idp-url option is specified and you are
not using a local copy of the IDP metadata.  You can now just use
the --saml-idp-url option, and we build the metadata URL from it.
This helps to minimize the number of required options when you are
registering an SP during installation.

https://fedorahosted.org/ipsilon/ticket/101

Signed-off-by: Nathan Kinder <nkinder@redhat.com>
Reviewed-by: Rob Crittenden <rcritten@redhat.com>