Unify the way backends are defined and loaded, unify the fs_cleanup function

mayan/apps/ocr/backends/__init__.py

@@ -1,28 +1,3 @@
-from __future__ import absolute_import
-
-import sys
-
-from django.utils.importlib import import_module
-
-from ..conf.settings import BACKEND
-
-
 class BackendBase(object):
     def execute(input_filename, language=None):
         raise NotImplemented
-
-
-def get_ocr_backend():
-    """
-    Return the OCR backend using the path specified in the configuration
-    settings
-    """
-    try:
-        module = import_module(BACKEND)
-    except ImportError:
-        sys.stderr.write(u'\nWarning: No OCR backend named: %s\n\n' % BACKEND)
-        raise
-    else:
-        return module
-
-ocr_backend = get_ocr_backend()