Add templating to initContainers and sidecarContainers

[yungwood]

Adds the ability for users to use templating within the initContainers and sidecarContainers values.

Summary of changes:

• renames existing extraDeploy.render helper function to tplRender
• removes multiple initContainers keys in deployment when initContainers is specified with rclone backups
• uses tplRender function to process initContainers and sidecarContainers
• add templating examples to values.yaml
• add initContainers, sidecarContainers and extraDeploy to values schema

[yungwood]

I created this MR because I was wanting to add minecraft-prometheus-exporter as a sidecar container and use templating functions to use the chart's rcon secret as an env variable.

[yungwood]

Sorry about that, chart version bumped