Joined Cases C-297/10 and C-298/10: Judgment of the Court (Second Chamber) of 8 September 2011 (references for a preliminary ruling from the Bundesarbeitsgericht (Germany)) — Sabine Hennigs (C-297/10) v Eisenbahn-Bundesamt, Land Berlin (C-298/10) v Alexander Mai (Directive 2000/78/EC — Articles 2(2) and 6(1) — Charter of Fundamental Rights of the European Union — Articles 21 and 28 — Collective agreement on pay for public sector contractual employees of a Member State — Pay determined by reference to age — Collective agreement abolishing the determination of pay by reference to age — Maintenance of established rights)