Create Nuxeo Jenkins CLI to wrap helm/jx commands

Create Nuxeo Jenkins CLI to wrap helm/jx commands in order to simplify the deployments in a build.

Identified commands:

• njx changeset find: list modified modules
• njx deploy <chart> [-n namespace]: deploy helm chart from museum + create namespace
• njx cleanup <chart> [-n namespace]: cleanup helm install + remove namespace
• njx vsc: Create VSC test file (not empty, otherwise it's ignore)
• njx vcs <envs...>: Prepare nuxeo-vsc test file
• njx preview: Rely on jx preview, wait for health check, comment PR with something like jx step pr comment --comment='Nuxeo Mongo Preview URL: $previewMongoUrl' -p $pullRequest.number -o $ORG -r 'nuxeo-notification-stream'