Uses UTIs to determine whether apps are installed or not

AltStore now inserts an app-specific UTI when resigning apps, and it periodically checks whether that app has been deleted by checking whether UTTypeCopyDeclaration returns nil for the same app-specific UTI.

AltKit/Bundle+AltStore.swift

@@ -18,6 +18,7 @@ public extension Bundle
         public static let appGroups = "ALTAppGroups"
         
         public static let urlTypes = "CFBundleURLTypes"
+        public static let exportedUTIs = "UTExportedTypeDeclarations"
     }
 }