Fix capitalisation of MusicBrainz everywhere

Make MusicBrainz consistently written as "MusicBrainz" and not
"musicbrainz" or "Musicbrainz".
Doesn't change instances that refer to the Python module or similar.

whipper/test/test_image_table.py

@@ -56,7 +56,7 @@ class LadyhawkeTestCase(tcommon.TestCase):
         # https://musicbrainz.org/cdtoc/attach?toc=1+12+195856+150+
         # 15687+31841+51016+66616+81352+99559+116070+133243+149997+161710+
         # 177832&tracks=12&id=KnpGsLhvH.lPrNc1PBL21lb9Bg4-
-        # however, not (yet) in musicbrainz database
+        # however, not (yet) in MusicBrainz database
 
         self.assertEquals(self.table.getMusicBrainzDiscId(),
             "KnpGsLhvH.lPrNc1PBL21lb9Bg4-")

whipper/test/test_image_toc.py

@@ -284,7 +284,7 @@ class CapitalMergeTestCase(common.TestCase):
 
     def testDuration(self):
         # this matches track 11 end sector - track 1 start sector on
-        # musicbrainz
+        # MusicBrainz
         # compare to 3rd and 4th value in URL above
         self.assertEquals(self.table.getFrameLength(), 173530)
         self.assertEquals(self.table.duration(), 2313733)