Feature: Ability to include overlays off of the main instructions file to better organize my content

[ahuffman]

As a user, I have many overlays. So many that my instructions files have grown quite large. I would like the ability to use an include keyword under commonOverlays, or yamlFiles[*].overlays, or yamlFiles[*].documents.overlays.

Example Instructions file:

commonOverlays:
  - include: /path/to/broken/out/overlays.yaml
yamlFiles:
  - name: my upstream manifests
    path: /tmp/downloads
    overlays:
      - include: /path/to/broken/out/overlays2.yaml
    documents:
      - name: specific document
        path: 0
        overlays:
          - include: /path/to/broken/out/overlays3.yaml

The files would contain arrays of overlays, without any indentation, and would be loaded up underneath the appropriate keywords commonOverlays and yamlFiles.

[ahuffman]

@JefeDavis I think this is what you were thinking when we discussed yesterday.