Support the language tag internally, so it can be used by plugins.

picard/formats/apev2.py

@@ -41,6 +41,7 @@ class APEv2File(File):
         "CatalogNumber": "catalognumber",
         "Barcode": "barcode",
         "EncodedBy": "encodedby",
+        "Language": "language",
         "MUSICBRAINZ_ALBUMSTATUS": "releasestatus",
         "MUSICBRAINZ_ALBUMTYPE": "releasetype",
     }

picard/formats/asf.py

@@ -89,6 +89,7 @@ class ASFFile(File):
         'genre': 'WM/Genre',
         'bpm': 'WM/BeatsPerMinute',
         'script': 'WM/Script',
+        'script': 'WM/Language',
         'mood': 'WM/Mood',
         'isrc': 'WM/ISRC',
         'copyright': 'Copyright',

picard/formats/id3.py

@@ -95,6 +95,7 @@ class ID3File(File):
         'TSOP': 'artistsort',
         'TSOT': 'titlesort',
         'TPUB': 'label',
+        'TLAN': 'language',
     }
     __rtranslate = dict([(v, k) for k, v in __translate.iteritems()])
 

picard/formats/mp4.py

@@ -92,6 +92,7 @@ class MP4File(File):
         "----:com.apple.iTunes:DISCSUBTITLE": "discsubtitle",
         "----:com.apple.iTunes:MOOD": "mood",
         "----:com.apple.iTunes:SCRIPT": "script",
+        "----:com.apple.iTunes:LANGUAGE": "language",
     }
     __r_freeform_tags = dict([(v, k) for k, v in __freeform_tags.iteritems()])