journals view, with new API route for journal facet, dynatable css factorized (applies for all corpora templates) and menu.html providing a corpora navbar to switch between journals and documents

[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

(couldn't get it to work with 3.5)

[FEAT] serializing of JSON is much better and has its own module
[CODE] upgraded to Python 3.5 (`traceback.TracebackException`)
[CODE] did some cleaning, here and there...

(cf. commit 93957939)

[FEAT] implemented a kind of simple front-end REST library

[FEAT] deletions now cascade