added tank.png mountain1.png mountain2.png mountain3.png and sorted alphabetically
added tank.png mountain1.png mountain2.png mountain3.png and sorted alphabetically


kongr45gpen/bzflag-import-1,kongr45gpen/bzflag-import-1,kongr45gpen/bzflag-import-1,kongr45gpen/bzflag-import-1,kongr45gpen/bzflag-import-1,kongr45gpen/bzflag-import-1