Take the Album Artist into account for Artist data

iTunesParser.py

@@ -131,10 +131,10 @@ class ITunesParser:
             Process artists in the track part of library and return a JSON formated for a bulk ELS request
         """
 
-        if 'Artist' not in track:
+        if 'Album Artist' not in track and 'Artist' not in track:
             return
 
-        akey = track['Artist']
+        akey = track['Album Artist'] if 'Album Artist' in track else track['Artist']
         # Add artist
         if akey not in self._artists:
             a_id = self.calc_id(akey)