What have you done

Lots of minor tidying up as well as a few bug fixes and features.

• Updated how error views are handled across dev and prod, CustomError is always displayed if used, DefaultError is used as the fallback, and MissingComponent is used if component is missing and it's dev.
• Added and improved tests for error view and cache purge handling
• Added http-status to handle our status codes properly
• Fixed Sometimes the 404 page doesn't return Status Code 404 #195 by sharing the error handling logic between fetch-data and handle-dynamic, rewrote the logic to be more succinct
• Fixed Pass through status data when rendering CustomError #134
• Found a bug with multiple endpoint error handling, logged at If route has multiple endpoints 404 API response isn't handled at all #212