Helm install MetacatUI as a separate chart and/or subchart

[artntek]

Metacat helm chart v1.0.0 optionally includes a metacatui instance that is co-deployed in the same container/tomcat instance as metacat.

In order to be able to replace existing production repos (knb, adc, hosted repos etc) with k8s versions, we need to be able to deploy and configure metacatui separately, in its own container. This could either be a subchart (for simplicity), or a separate chart altogether (since it's not a metacat dependency).

@mbjones has created a proof-of-concept as detailed in the MetacatUI Issue "helm chart to deploy metacatui on kuberntes #2368"