Schema's loaded from other than requested file don't store location

[maxlepikhin]

setResolve(true) tells OpenAPIV3Parser to load specs from external locations and put them in the model.

  ParseOptions parseOptions = new ParseOptions();
  parseOptions.setResolve(true);
  OpenAPI openApiModel = new OpenAPIV3Parser().read(inputFile, null, parseOptions);

It is desirable to distinguish schemas loaded from external locations from the ones defined locally. For example:

• errors.yaml may define shared error types.
• api1.yaml and api2.yaml (that reference errors.yaml) may define two different APIs.
  Code generation for errors.yaml should only be done once.

On the other hand, api3.yaml may reference another file.yaml that must be resolved and included in the generated code for api3 unlike errors.yaml.

Proposal: store original reference in $originalRef next to $ref in SchemaProcessor.

This change will let code generators add custom logic for shared vs not schemas.