Wizard UX fixes

Fixed cancelEvent slot, disabled back butttons, removed close button since cancel button displays alert and can close app instead of loading GUI with light server error.

src/firsttimewizard.h

@@ -23,11 +23,10 @@ public:
     QString _seed;
     void setSeed(QString Seed); 
     void setBirthday(QString Birthday);   
-    void cancelEvent();
 
 public slots: 
     void slot_change_theme(const QString& themeName);
-    
+    void cancelEvent();
 
 protected:
     int nextId() const;