Expose middleware properties in activity/orchestrator

[twsouthwick]

The properties bag from DispatchMiddlewareContext contains information that might be useful from activities/orchestrators. However, they currently do not show up from those context options. This change plumbs the dictionary through and surfaces it for both activities and orchestrators.

As part of this, the following changes are introduced to show a use case for sharing properties:

• A new interface IContextProperties is added that just has the properties dictionary. However, this allows for shared code to set and get properties by type or by name.
• A .Properties member is added to the activity and orchestration contexts
• The serializers for messages and errors are retrieved from the .Properties so that they can be configured in middleware

If it would be easier to have just the properties change, I can separate the serializer change out.

[davidmrdavid]

/azp run

[azure-pipelines[bot]]

Azure Pipelines could not run because the pipeline triggers exclude this branch/path.