Update `failed_jobs` table to add missing `uuid` column.

[ericp-mrel]

This also updates the payload and exception columns to be inline with default the laravel migration.

Fixes #696

Let me know if you'd prefer I remove the updates to the payload and exception columns.

[LukeTowers]

@ericp-mrel looks good to me, were you able to test it running locally?

[ericp-mrel]

@LukeTowers

I've tested it locally with a blank Winter CMS project, created a job class that fails so it gets added to the failed_jobs table and is working correctly. I also tested by importing a database dump from one of my other projects (Winter CMS v1.1) and ran the migrations against that database and the migrations run successfully for existing projects as well.