Problems with external references

[olafnielsen]

There are some problems with the swagger-viewer when referencing other files:

• When a reference cannot be found, the preview is either a blank page or a previously generated page.
• Sometimes the references are missing or referring components they are not dependent on. Example:

...is the preview of two yaml files (ignore the text extension):

file-with-external-references.yaml.txt another-file.yaml.txt

Expected result should look something like this: file-without-external-references.yaml.txt