ENYO-2344: genZip works behind HTTP proxies

- Implement `/config` web endpoint & associated async configuration
  flow.
- Use proper npmlog
- Fix error handling
  - Use HttpError from library
  - Put error handler at the right position
  - Stop wrapping native errors (let errorHandler do it)

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