Backport (7.8) Support Roles on sitemenuitems

sitemenu items should be possible to be visible only for users in the right role.

Currently, you need to decorate all HstSiteMenuItemImpl to be able to achieve this and mis0use hst:parameternames/values

Support in hst for this is trivial, but really needed to support better authorization based sites which of course include authorization in sitemenu items