Event Store Improvements for V4

[jeremydmiller]

This replaces #1307, but see the original conversations there.

Also see @wastaz's comments.

Big Improvements

• Improved Projection Support
• Event Metadata
• Async Daemon Improvments
• Partitioning Support for the Event Store
• Improved optimistic versioning of event stream append operations
• Mechanism to Import Events from external systems
• Improved inline projections and event capture
• Projection Snapshots
• Stream Archiving
• Event versioning and upcasting

Tactical Changes

• Event Store Feature Schema
• Aggregate Stream for missing stream
• StartStream() should enforce the stream is new
• Using a long for the event sequence id
• Stream locking for better event store concurrency
• Recipe for easy testing of event projections

[oskardudycz]

@jeremydmiller we should also consider #1639.

[jeremydmiller]

This epic story is reflected now in smaller stories. I'm closing just to make this list smaller.