Operator bundle readme should be editable as a markdown file

[babbageclunk]

Describe the current behavior
The installation instructions for the operator bundle are embedded in config/operator-bundle/bases/azure-service-operator.clusterserviceversion.yaml at the moment. That makes them hard to maintain and makes it more likely that they get out of sync with our regular installation instructions.

Describe the improvement
After the generation changes in #1416, the installation instructions should be inserted into the generated yaml from a regular markdown file under the docs directory.

[babbageclunk]

From discussion on #1410

[matthchr]

Originally this was filed for ASOv1, but it applies to ASOv2 too! We don't have an operator bundle for v2 yet but once we do, this will be required as well.

[matthchr]

We still want to do this

[matthchr]

We still want to do this