ENYO-2955: change pre-version scheme from `M.m.p-X` to `M.m.p-pre.X`

This is less confusing than the previous scheme & it is also a format
supported by http://semver.org & NPM.

Enyo-DCO-1.1-Signed-off-by: Francois-Xavier KOWALSKI <francois-xavier.kowalski@hp.com>
ENYO-2955: shells is a dev-time dependency, not run-time

…and it should remain this way!

Enyo-DCO-1.1-Signed-off-by: Francois-Xavier KOWALSKI <francois-xavier.kowalski@hp.com>
ENYO-2955: skeleton for `scripts/release.js`

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