Synthesis and antimicrobial properties of new 4-(alkylidene/arylidene)amino-5-(2-furanyl)-2,4-dihydro-3H-1,2,4-triazole-3-thiones and 6-aryl-3-(2-furanyl)-7H-1,2,4-triazolo[3,4-b][1,3,4]thiadiazines