[FEATURE] The 'extract_ngrams' method is now available from the queryset as well
[BUGFIX] The parsed resources are now marked as parsed in the database

Still needs to be fully tested.

Work in progress...

...just need to add some elements in RisFileParser._parameters and IsiFileParser._parameters.

Now, create some mother class to allow RIS as well.
Also, integrate more fields.

- Added some tests for Notebook

Merge maste