add dependency graph on sentences

[mgogoulos]

a more light way as displaCy does it would also be beneficial on the sentences section

[giannisdaras]

Working on it. We can use displaCy itself for that reason.
displaCy outputs html markup but it's too slow to run on the whole corpus at once.
I am working on a visualize it button next to each sentence which on click redirects to a visualization page for the sentence.

[giannisdaras]

Done