Case C-46/15: Judgment of the Court (Fifth Chamber) of 7 July 2016 (request for a preliminary ruling from the Tribunal Central Administrativo Sul — Portugal) — Ambisig — Ambiente e Sistemas de Informação Geográfica SA v AICP — Associação de Industriais do Concelho de Pombal (Reference for a preliminary ruling — Public procurement — Directive 2004/18/EC — Article 48(2)(a)(ii), second indent — Technical abilities of economic operators — Direct effect — Means of evidence — Hierarchical relationship between the private purchaser’s certification and the tenderer’s unilateral declaration — Principle of proportionality — Prohibition on introducing substantive changes to the means of evidence provided for)