Extend default SAML IdP metadata validity period
    
    Our current default IdP metadata validity period is hardcoded to 30
    days.  This is very limiting for anything other than a test environment
    unless there is a way to allow SPs to automatically fetch updated metadata
    on a regular interval.
    
    This patch increases the default validity period to 5 years.  In addition,
    a new option for ipsilon-server-install is provided to allow a different
    validity period to be specified.
    
    https://fedorahosted.org/ipsilon/ticket/103
    Signed-off-by: Nathan Kinder <nkinder@redhat.com>
    Reviewed-by: Patrick Uiterwijk <puiterwijk@redhat.com>