Allow EventSourceID and PartitionID to be strings instead of Guids using Contracts v6.0.0, and fix little Embedding bug

[woksin]

Summary

Implementing the changes introduced by https://github.com/dolittle/Contracts/pull/53. Allowing EventSourceID and PartitionID to be strings, to more easily integrate with events from existing systems.

Also fixed a small bug when returning an array of events from an Embedding Update/Delete method.

This is considered a breaking change because it requires a Runtime compatible with Contracts v6 to function.

Added

• EventSourceID is now a string instead of a Guid.
• PartitionID is now also a string instead of a Guid.

Fixed

• Aligned names of event type fields throughout messages from Contracts v6.0.0
• Allow Embedding Update/Delete method to return an array of events.