Add app directory check

Fixes #77

Secretive/Controllers/ApplicationDirectoryController.swift

@@ -0,0 +1,22 @@
+import Foundation
+
+struct ApplicationDirectoryController {
+}
+
+extension ApplicationDirectoryController {
+
+    var isInApplicationsDirectory: Bool {
+        #if DEBUG
+        return true
+        #else
+        let bundlePath = Bundle.main.bundlePath
+        for directory in NSSearchPathForDirectoriesInDomains(.applicationDirectory, .allDomainsMask, true) {
+            if bundlePath.hasPrefix(directory) {
+                return true
+            }
+        }
+        return false
+        #endif
+    }
+
+}