Create Helm chart for PravegaCluster

[adrianmo]

We currently have a Helm chart for deploying the operator, but we are missing a full-featured chart that creates all needed resources and deploys a Pravega cluster. The resources that this chart needs to manage are the following:

• PravegaCluster CRD
• Operator deployment
• Operator service account
• Operator role
• Operator clusterrole
• Operator rolebinding
• Operator clusterrolebinding
• PravegaCluster CR

All these resources can be currently found at the deploy/ directory. These manifests need to be transformed into chart templates to make them configurable.

As a first version of the chart we don't need to make it fully configurable, but at least we need to be able to configure the following options:

• cluster name
• version
• image repository
• replicas for BK, SS, and C

As a reference, we can take a look at other Helm charts in https://github.com/helm/charts/tree/master/stable.