Refactor the converter app

Don't cache the entire converter class to lower memory usage.
Instead a get_converter_class() function is now provided to
load the converter backend class.

Add model permission inheritance to transformations to
removel custom permission checking code in the views.

User keyword arguments.

Update URL parameters to the '_id' form.

Add missing edit and delete icons. Improve the create
icon using composition.

Update add to comply with MERCs 5 and 6.

Signed-off-by: Roberto Rosario <Roberto.Rosario@mayan-edms.com>

mayan/apps/converter/apps.py

@@ -1,8 +1,8 @@
 from __future__ import unicode_literals
 
-from django.utils.encoding import force_text
 from django.utils.translation import ugettext_lazy as _
 
+from mayan.apps.acls.classes import ModelPermission
 from mayan.apps.common import MayanAppConfig, menu_object, menu_sidebar
 from mayan.apps.navigation import SourceColumn
 
@@ -25,12 +25,20 @@ class ConverterApp(MayanAppConfig):
 
         Transformation = self.get_model(model_name='Transformation')
 
-        SourceColumn(attribute='order', source=Transformation)
+        ModelPermission.register_inheritance(
+            model=Transformation, related='content_object'
+        )
+
         SourceColumn(
-            source=Transformation, label=_('Transformation'),
-            func=lambda context: force_text(context['object'])
+            attribute='order', include_label=True, source=Transformation
+        )
+        SourceColumn(
+            attribute='get_transformation_label', is_identifier=True,
+            source=Transformation
+        )
+        SourceColumn(
+            attribute='arguments', include_label=True, source=Transformation
         )
-        SourceColumn(attribute='arguments', source=Transformation)
 
         menu_object.bind_links(
             links=(link_transformation_edit, link_transformation_delete),