DS-1028 - CAS and SAML implementation

CAS Authentication with optional SAML attribute values dicovery for DSpace 5_x.

The first patch was formerly implemented by Kaboré Wendin-Malegdé Patrick at JIRA (https://jira.duraspace.org/browse/DS-1028) and further user kgunn at JIRA did some arrangements to make it work with DSpace 1.8.2 and CAS 3.1.x. Finally nkneumann updated it to work with DSpace 3.1 (nkneumann@53e02e1).

This patch extends the work done by nkneumann by fixing it for DSpace 4_x and 5_x and allowing usage of SAML to get user attributes.