Add parameterization support - will support the generation of OpenShift Templates and Helm Charts

[jstrachan]

i.e. figure out a way to define parameters and then refer to them in the kedge file using some kind of syntax, such as ${FOO} that then gets passed through into the generated OpenShift Template or Helm Chart - but get replaced by environment variables and/or default values when generating a vanilla kubernetes YAML.

We need to be careful that parameter expressions don't clash with environment variable expressions for things like versions https://github.com/kedgeproject/kedge/issues/224

[surajssd]

There was some discussion of parameterization of ingress https://github.com/kedgeproject/kedge/issues/41

We can have a general parameterization support in Kedge for kedge files (which is talked of https://github.com/kedgeproject/kedge/issues/224 and https://github.com/kedgeproject/kedge/issues/41) and then some parameterization support that is carried forward in OpenShift templates which is mentioned in this issue.

[cdrage]

Hey @surajssd @kadel can we close this since https://github.com/kedgeproject/kedge/pull/535 was pushed?

[surajssd]

@cdrage parameterization is added but i am not sure of helm chart or openshift template generation