Add python tekton pipeline demo

[KevinMGranger]

This adds a basic python-based tekton demo in the demo dir, and a script to set it up and run it.

This is separate from the work in #333 because we should merge early and merge often. #333 will be a big enough PR on its own, so separating this will help with readability.

This is not documented in the docs/Demo.md page because we should have the tekton functionality in pelorus up and running first.

Closes #331.

Testing Instructions

1. Make sure:

• oc and tkn are installed
• you're logged in to the cluster
• you have permission to install operators and create projects

2. run `./demo/demo-tekton

You should eventually see a simple page served at the link referenced in the output.

Continuing with the script as normal should eventually show changes to that page.

@redhat-cop/mdt

[mpryc]

LGTM