The Austro-Hungarian U-boat fleet during the First World War, mainly consisted of German manufactured units transported by rail from Germany's northern shipyards to the Austrian ports on the Adriatic Sea, following the end of the war in 1918, all Austrian submarines were surrendered to the powers of which understanding, linking the Russian Empire, the French Third Republic, and the United Kingdom of Great Britain and Ireland after the signing of the Anglo-Russian Entente on 31 August 1907, is called?