Respect media extension in URL

[AlenPelin]

When having several same-name media items with different extensions, the request extension must be taken into account when picking one of them prior to apply sort order.

Scenario:

1. Upload two different images with image.png and image.jpg names to Sitecore
2. Request /-/media/image.png and /-/media/image.jpg

Actual Result:
Both images are the same

Expected Result:
The images are different and corresponding