Added Devfile Demo

[sleshchenko]

This is PR that contains Devfile Demo.
It's a demo that shows how to create Devfile for live application with chectl and then how to use it.

Faced issues

• Che uses not latest version of Che Theia by default. Fixed by Update default Theia IDE version to 'next' eclipse-che/che#13235
• Plugin Registry was broken. Fixed by Fixed permissions for v2 folder eclipse-che/che-plugin-registry#134
• Unable to set up entrypoint for application container during generate Devfile phase.
  It's needed to edit generated devfile to make it usable for development. Nice to improve this part.
• Permissions on OpenShift. Application works fine on image that was used initially node:12.0-alpine, but there are issues(unable to perform some commands in terminal) in workspace because of anyuid.
• Wait for mongo with init container. There is an issue in workspace if application has init containers
  that waits for another component, like mongo database. This topic should be investigated more. Maybe it's good enough just to manually remove init containers is such case.
• There is no way to bound projects sources to application container. Support mountSources for non-plugin tools in devfile eclipse-che/che#12554 should be implemented to avoid including projects PVC to application deployment
• Different arguments for deploying Che with chectl, auto pick up CHE_ env vars. Now script.md use deploy_che.sh script since it more convenient since it has such feature.
• This demo is designed to be suitable for Kubernetes and OpenShift. Ingress is used to make the application available. But Ingress has an issue since host should be hardcoded. So, you have to update host if your K8s/OS installation host is different from 192.168.99.100 and you're not able to deploy two NodeJS application in two different namespaces.
• There is no any output during starting of a workspace using GitHub URL based factory. Fix printing of runtime output during factory accepting eclipse-che/che#13332

[sleshchenko]

@dneary I cannot request a review from you, but your review would be useful as well.

[dneary]

@dneary I cannot request a review from you, but your review would be useful as well.

I think I fixed it... I joined the project. I had missed @l0rd's invitation.

[sleshchenko]

After discussion with @l0rd was decided to merge this PR as is since there are a couple of people who are reusing this demo and doing it from the master branch is more convenient.
Feel free to comment this PR and I will create fixes in new PR, or create PRs by yourself.