only duplicate notes with diff schema in anki1 import (#612)

anki/importing/anki1.py

@@ -9,6 +9,8 @@ from anki.importing.anki2 import Anki2Importer
 
 class Anki1Importer(Anki2Importer):
 
+    dupeOnSchemaChange = True
+
     def run(self):
         u = Upgrader()
         # check

anki/importing/anki2.py

@@ -17,6 +17,7 @@ class Anki2Importer(Importer):
     needMapper = False
     deckPrefix = None
     allowUpdate = True
+    dupeOnSchemaChange = False
 
     def run(self, media=None):
         self._prepareFiles()
@@ -110,7 +111,7 @@ class Anki2Importer(Importer):
         srcMid = note[MID]
         dstMid = self._mid(srcMid)
         # duplicate schemas?
-        if srcMid == dstMid:
+        if srcMid == dstMid or not self.dupeOnSchemaChange:
             return origGuid not in self._notes
         # differing schemas
         note[MID] = dstMid