Create edge service packaging format to enable copying services

[t-fine]

There is a poor man's example of copying services in https://raw.githubusercontent.com/open-horizon/examples/master/tools/loadResources . But a better approach is for us to define a packaging format for service definitions (and associated patterns and deployment policies):

• tar format that holds the horizon dir
• when we build the pkg, we push the built images to docker hub and include a reference in the pkg. Or we docker save the images to tar files and include them in the pkg.
• add list of arches to horizon dir?
• add post-publish script?
• hzn sub-cmd to publish 1 service-pkg or a tar file of them:
  • 1st implement in script (both build pkg and publish pkg), then convert to hzn sub-cmd
  • unpacks and runs: hzn exchange service publish -O -P -f horizon/service.definition.json
  • also optionally publishes: pattern, dep pol, service pol
• hzn sub-cmd to get a service from the exchange and package it
• The enables a user to copy services from 1 org to another, or 1 exchange to another

As a reference, there is a sample telco pkging format: https://www.etsi.org/deliver/etsi_gs/NFV-SOL/001_099/004/02.07.01_60/gs_NFV-SOL004v020701p.pdf