Added nexus blob data building script.

Added nexus blob data building script.

Script can be used to pre-build nexus data blob from given binary files
at build time to avoid nexus populating each time from empty state
at installation time. This is usefull when most of the binaries are
changed rarely and nexus can be just started up with pre-build blob
data at installation time.

Currently just docker images and NPM packages are supported.

Script is generic and should not have any dependency to ONAP as such
but there is few lines now that are rererring to onap, see below grep:

$ grep -i onap build_nexus_blob.sh
SIMUL_HOSTS="docker.elastic.co gcr.io hub.docker.com nexus3.onap.org nexus.onap.org registry.hub.docker.com ${NEXUS_DOMAIN}"
def r = repository.createDockerHosted("onap", 8082, 0)
sed -i "s|https://nexus.onap-me.novalocal|http://${NEXUS_DOMAIN}:8081|g" package/package.json

Change-Id: I008678fdd6dc067e7ecb26969225e2324b44e7ba
Issue-ID: OOM-1551
Signed-off-by: Samuli Silvius <s.silvius@partner.samsung.com>