ENYO-1740: update Node.js modules layout

- ARES will be shipped as an NPM module, so it makes senses to have
  a top-level `node_modules` that contains modules shared by `hermes/`
  and `test/server/`

Enyo-DCO-1.1-Signed-off-by: Francois-Xavier KOWALSKI <francois-xavier.kowalski@hp.com>