Add support for YAML configuration files. Add support for editing setting options and saving them using the new YAML configuration file support. Add new revertsettings management command. Add new permission to edit setting via the UI.

Signed-off-by: Roberto Rosario <roberto.rosario.gonzalez@gmail.com>

mayan/apps/document_signatures/settings.py

@@ -16,5 +16,5 @@ setting_storage_backend_arguments = namespace.add_setting(
     global_name='SIGNATURES_STORAGE_BACKEND_ARGUMENTS',
     default='{{location: {}}}'.format(
         os.path.join(settings.MEDIA_ROOT, 'document_signatures')
-    )
+    ), quoted=True
 )