[FEAT] linked nodes with links (cf. `gargantext.constants` and `gargantext.models.Node.as_list()`
[FEAT] implemented an `ngrams` pseudo-attribute on `gargantext.models.Node` (available from REST api)
[FEAT] on REST API, renamed GET parameter `type[]` to `types[]`
[FEAT] `json_dumps()` can even serialize SQLAlchemy models and models now