Improve folksonomy tag comparisson for ignored tags.

Use full tag names and not substrings for comparisson so that e.g. ignoring "someothertag,hip hop rap" does not also ignore "rap". Also this change makes the comparisson case insensitive to match the behavior on MB.org.

Fixes PICARD-335

picard/track.py

@@ -144,10 +144,10 @@ class Track(DataObject, Item):
         # And generate the genre metadata tag
         maxtags = config.setting['max_tags']
         minusage = config.setting['min_tag_usage']
-        ignore_tags = config.setting['ignore_tags']
+        ignore_tags = self._get_ignored_folksonomy_tags()
         genre = []
         for usage, name in taglist[:maxtags]:
-            if name in ignore_tags:
+            if name.lower() in ignore_tags:
                 continue
             if usage < minusage:
                 break
@@ -158,6 +158,13 @@ class Track(DataObject, Item):
             genre = [join_tags.join(genre)]
         self.metadata['genre'] = genre
 
+    def _get_ignored_folksonomy_tags(self):
+        tags = []
+        ignore_tags = config.setting['ignore_tags']
+        if ignore_tags:
+            tags = [s.strip().lower() for s in ignore_tags.split(',')]
+        return tags
+
 
 class NonAlbumTrack(Track):