ENYO-2344: implement & document `files:[]` templates

- It is now possible to copy directly files from the template provider
  source tree into the target project source tree, without the need for
  an intermediate ZIP-file.  This is useful for small libraries like
  widget or Enyo-wrappers that come in addition to existing libraries.

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