OpenWhisk should provide the sequence activation id when an action is invoked via a sequence

Per discussion with @csantanapr on Slack, actions can get access to the ID of their current activation, but *not* the ID of a sequence if they happen to be running inside one. That data should be visible as well.

No files, tests, or entry points are named. Start by tracing how an action receives its current activation ID and how sequence-invoked actions receive invocation metadata; done means an action running inside a sequence can also access the sequence activation ID.

Written by the indexing model from the issue text.