Update the database in a different thread so it doesn't freeze the main

thread.
Show PIN in a dialog instead of a notification popup.
Translations updated.

avdecoder.h

@@ -36,14 +36,17 @@ class AVDecoder
 public:
     AVDecoder();
     ~AVDecoder();
+
     bool open(const QString filename);
+    void close();
+
     QByteArray getAudioThumbnail(int width, int height);
     QByteArray getVideoThumbnail(int width, int height);
     void getPictureMetadata(metadata_t &metadata);
     void getAudioMetadata(metadata_t &metadata);
     void getVideoMetadata(metadata_t &metadata);
-    void close();
 
+    // simulate a static constructor to initialize libav only once
     class AvInit
     {
     public: