Package demo boot scripts into nexus artifact

Package the scripts in the boot/ directory
into a zip file to be deployed to nexus, so
that they can go through the normal artifact
release process and become available from
https://nexus.onap.org/content/repositories/releases/
repo.

Change-Id: Idbb573068eb79686677aa47e84e217a2d626e3fc
Issue-ID: INT-504
Signed-off-by: Gary Wu <gary.i.wu@huawei.com>