NodePagingList type should include optional "source" property

[chris-equis]

Type of issue: (check with "[x]")

- [ ] New feature request
- [x] Bug  
- [ ] Support request

Current behavior:

NodePagingList interface does not have optional source property as MinimalNodeEntityEntry

Expected behavior:

Property has to be described by the interface as optional

Steps to reproduce the issue:

1. Make request
   GET https://api-explorer.alfresco.com/alfresco/api/-default-/public/alfresco/versions/1/nodes/-root-/children?includeSource=true

2. Observe the response

{
    list: {
        pagination: {},
        entries: [],
        source: {}
    }
}