[FIX] Add search icon. TODO: implement search and remove links towards commercial searchs (science is agnostic many thanks for your comprehension.)

[FIX] Database capacity detected for Text Indexing. 2 paths for next steps: hash indexing and text (postgresql) indexing.

fixed local tfidf to compute (doc, ngram) similarities and NOT cumulated scores per ngram (TODO: discuss parallel changes for global tfidf)

       USAGE: methode DELETE : /api/nodes?ids=1,2,3

[FIX] Clean code after exploration.