Added npmVersion to install NPM

Added npmVersion to install NPM

To install local copy of npm, needed to make 2 changes to
frontend-maven-plugin configuration:

1) Add tag <npmVersion>6.4.1</npmVersion>
2) Removed tag <npmDownloadRoot>

Confirmed in local build that those changes result in npm being installed
in local 'node' directory (which it was not before these changes).

Also, changed parent version to 1.3.1-SNAPSHOT - this will be needed to
prevent builds from breaking when new SAN certs are installed for ONAP gerrit.

Change-Id: I576d8737eccfaa3024a36608edc1102535a55d26
Issue-ID: CCSDK-1491
Signed-off-by: Timoney, Dan (dt5972) <dtimoney@att.com>