[grouper-shib] support the attribute framework in filters

See https://lists.internet2.edu/sympa/arc/grouper-users/2011-02/msg00034.html

edu.internet2.middleware.grouper.shibboleth.filter.ExactAttributeGroupFilter

public boolean matchesGroup(Group group) {
try

{ return value.equals(group.getAttributeOrFieldValue(name, true, false)); }

catch (AttributeNotFoundException e)

{ return false; }

}