Fix grafana Makefile, Procfile template, and update docs

What does this Merge Request do?

Updates grafana Makefile so:

• Uses latest available version.
• Uses binaries instead of source.
• Is much simpler.

MR also:

• Updates Procfile template, so can be properly controlled from gdk.yml.
• Makes small documentation update, so that this method of standing up Grafana is at least mentioned.
• Removes sample configuration, because default configuration works well enough.

Closes: #1143 (closed)

CC @mjwood

Merge Request checklist

• Tests added for new functionality. If not, please raise Issue to follow-up.
• This change is backward compatible. If not, please include steps to communicate to our users.
• Documentation added/updated, if needed.
• gdk doctor test added, if needed.