[MSG OK] better error handling between server-side graph generation and the error messages shown on client-side

Rename our server-side "graphExplorer" app to "graph", in order to prevent confusion with client-side tina-based graphExplorer from static/lib

(recuperation de la nouvelle façon d'envoyer des messages + statut HTTP pour utilisation côté graphExplorer)

[MERGE OK] added small readme and removed old symlinks to tinawebJS in gargantext_lib (not necessary anymore)

git-subtree-dir: static/lib/graphExplorer
git-subtree-mainline: 3bfb7073
git-subtree-split: d256049a

integrate recent post-refactoring gargantext changes to *extras_explorerjs* (new paths for corpora, intersection, node deletion and static imgs)

add debug traces to each function, remove trailing spaces in scripts, add initialization call graph schema

fix bulk_insert_ifnotexists occasional bugs with better term normalization sequence and reduce frequency of integrate step (reduce DB effort but use slightly more RAM)