Align iter8 to match terminology used in docs

[Alan-Cha]

With v0.16, a number of concepts have been removed, which have been eliminated in the docs but not in iter8

For example:

• The metric server expects an experiment query parameter for both the HTTP and gRPC dashboards, but the term experiment has been removed from the documentation. Some alternatives would be test or performanceTest.

  Query string: namespace=default&experiment=default

• The slack and github tasks (which under the covers is the notify task) both use a payload template that has access to a .Report field. The documentation makes no mention of this. The documentation makes mention of an experiment summary, however.