show skip button only in travel intro, if user traveled

enzevalos_iphone/IntroDescriptionViewController.swift

@@ -107,7 +107,7 @@ class IntroDescriptionViewController: UIViewController, IntroInfoButton {
         if doneAction != nil {
             self.navigationItem.setRightBarButton(UIBarButtonItem(title: doneText, style: .plain, target: self, action: #selector(doneTapped(_:))), animated: true)
         }
-        if skipAction == nil {
+        if skipAction == nil || !(UserManager.loadUserValue(.userTraveled) as? Bool ?? false)  {
             skipButton.isHidden = true
         } else {
             skipButton.isHidden = false

enzevalos_iphone/TravelHandler.swift

@@ -476,6 +476,7 @@ public class TravelHandler {
                 //TODO: errorhandling
             }
             describeSecretController.navigationController?.pushViewController(secretController, animated: true)
+            UserManager.storeUserValue(true as AnyObject, attribute: .userTraveled)
         }
         secretController.navigationItem.hidesBackButton = true
         secretController.doneText = NSLocalizedString("Next", comment: "present next ViewController")

enzevalos_iphone/UserData.swift

@@ -22,7 +22,7 @@ import KeychainAccess
 
 
 enum Attribute: Int {
-    case accountname, userName, userAddr, userPW, smtpHostname, smtpPort, imapHostname, imapPort, prefEncryption, publicKey, autocryptType, imapConnectionType, imapAuthType, smtpConnectionType, smtpAuthType, sentFolderPath, draftFolderPath, trashFolderPath, inboxFolderPath, archiveFolderPath, nextDeadline/*used for Logging; determines the earliest next time a log is send to the researchers*/, prefSecretKeyID, subjectSalt /*used for Logging; salt for the hashfunction for mail subjects*/, loggingFolderPath
+    case accountname, userName, userAddr, userPW, smtpHostname, smtpPort, imapHostname, imapPort, prefEncryption, publicKey, autocryptType, imapConnectionType, imapAuthType, smtpConnectionType, smtpAuthType, sentFolderPath, draftFolderPath, trashFolderPath, inboxFolderPath, archiveFolderPath, nextDeadline/*used for Logging; determines the earliest next time a log is send to the researchers*/, prefSecretKeyID, subjectSalt /*used for Logging; salt for the hashfunction for mail subjects*/, loggingFolderPath, userTraveled
 
     var defaultValue: AnyObject? {
         switch self {
@@ -44,6 +44,8 @@ enum Attribute: Int {
             return Date(timeIntervalSinceNow: TimeInterval(Logger.loggingInterval)) as AnyObject?
         case .loggingFolderPath: //save backendFolderPath here
             return "letterbox-study" as AnyObject?
+        case .userTraveled:
+            return false as AnyObject?
         default:
             return nil
         }