Task updates

**WIP:** This is a work-in-progress and is not ready to be merged yet.

## Overview

Provides a way for clients to attach status updates to tasks they are working on. The contents of the status is an opaque blob that skuld has no understanding of.

The status updates are stored in the claim as a vector and it is up to the client to provide the index of the next available index in the `logs` vector.

Fixes #18