Add option to force upgrade when install is tracking latest version

[claycooper]

If no version is specified in the HelmChart resource it's not possible (or not documented) how to trigger an upgrade without changing an inconsequential value in the spec. A possible solution would be to add a force flag to the spec that the controller sets to false after successful completion or watch for a specific annotation to trigger an upgrade. Alternatively, having documentation that says "here's a safe key in the spec that you can modify to trigger an upgrade.

[brandond]

You can just change the whitespace or a comment in the valuesContent... At the moment the controller does not have any functionality to actually poll the repo for changes to the chart.

[claycooper]

I'm not looking for the controller to look for changes in the chart repos. I'm looking for a way to have the controller run the install/upgrade for the latest chart without specifying the version. With Helm CLI I'd run helm upgrade foo with my CD tooling but I can't do that using helm-controller since the HelmChart needs to notice a change. I'd be happy with having the controller running when a specific annotation, like lastUpgraded, is modified on an existing object.