Streamline Helm chart release (#730)

* Add Kubernetes 1.9+ as prerequisite to Helm chart

* Provide GitHub release title

* Tweak GitHub release for Helm Charts

build/azure-devops/agents-scraper-release-official-helm.yml

@@ -4,7 +4,8 @@ resources:
 trigger: none
 pr: none
 variables:
-  Release.TagName: 'Helm-$(Helm.Chart.Version)'
+  Release.TagName: 'helm-$(Helm.Chart.Version)'
+  Release.Title: 'Helm v$(Helm.Chart.Version) for Promitor Scraper v$(Helm.App.Version)'
   # Helm.App.Version is configured in the build definition as settable at queue time
   # Helm.Chart.Version is configured in the build definition as settable at queue time
 stages:

charts/promitor-agent-scraper/README.md

@@ -15,6 +15,7 @@ This chart bootstraps a **Promitor Scraper Agent** deployment on a Kubernetes cl
 
 ## Prerequisites
 
+- Kubernetes v1.9 or above
 - Azure Subscription
 - Azure AD Application to authenticate with ([docs](https://promitor.io/configuration/#authentication-with-azure-monitor))