Default storage class name and config map name in helm should depend on installation name

[akantak]

When trying to create two storage classes with different config maps, do not download https://raw.githubusercontent.com/rancher/local-path-provisioner/master/deploy/local-path-storage.yaml and customize that. There is a lack of a few configuration options there, like --service-account-name, --provisioner-name and --configmap-name in container command there.
Use the helm chart that is placed here with customized config map's name and values, storage class name, etc.

Linking #152 as it has common parts.

P.S. There should be mentioned in the main README.md file that the helm chart exists and is documented inside repo.

[akantak]

Linking also #89 as this issue describes enhancement for helm chart