Documentation: Document the various config parameters and their use case

[akodali18]

Need to document the configuration params in https://github.com/vmware/wavefront-adapter-for-istio/blob/master/install/wavefront/values.yaml#L15 in more detail. (especially for "prefix")

[venilnoronha]

This is documented in some detail at https://github.com/vmware/wavefront-adapter-for-istio/tree/master/install/wavefront#configuration-parameters. It'd be great to add more details, and maybe an example to make it more clear.

[akodali18]

From your suggestion offline - "it’d be good to have a separate document with more detailed explanation of the configuration options. We can link to this new doc in both the standard and the Helm readmes."

[shawnho1018]

Thanks both. I think examples would work better or at least an explanation to show how the adapter works. I guess it re-direct matched "metrics tag" and "prefix to prepend all metrics" to wavefront perhaps?