Support subword and word language models

Closes #199 (closed)

Ref https://redmine.teklia.com/issues/4941

dan/ocr/predict/prediction.py

@@ -510,6 +510,7 @@ def run(
     dan_model.load(
         model, parameters, charset, mode="eval", use_language_model=use_language_model
     )
+    batch_size = 1 if use_language_model else batch_size
 
     # Do not use LM with invalid LM weight
     use_language_model = dan_model.lm_decoder is not None