Added support for data_relation nested in lists

[pdecat]

This PR adds support for data_relations nested in lists.

This resolves errors similar to the following one in the swagger editor:

 Swagger Error
Reference could not be resolved: #/definitions/deployment__id
Jump to line 543
Details
 Object
code:  "UNRESOLVABLE_REFERENCE"
message:  "Reference could not be resolved: #/definitions/deployment__id"
 path: Array [8]
error:  "JSON Pointer points to missing location: #/definitions/deployment__id"
level: 900
type:  "Swagger Error"
description:  "Reference could not be resolved: #/definitions/deployment__id"
lineNumber: 543

Best regards, Patrick.

[pdecat]

Reworked this PR a bit to avoid processing lists not containing schemas.

[nicolaiarocci]

Thanks