#4 Support for credential delegation using S4USelf

[Richard Pointon]

The patch adds the ability for the filter to use the S4USelf Kerberos protocol extension to get a set of delegated credentials for the user when they are not forwared by the client. To build the patch you will need to use JDK 8 or later that has support for MS-S4U. Also you will need setup the pre-auth account in AD to use constrained delegation and select the use any protocol option.