Visualization for HTTP errors AB#138

[BradGardea]

When attempting to submitting a file I discovered through Developer Console -> Network that the page was actually throwing an internal server error (HTTP 500) when making the request to submit a file. This error went away after ~10 minutes, however it was still an issue to try to figure out if I was causing the problem or if it was an external problem with MarkUS.

I would propose some sort of visual support for basic HTTP errors in order to prevent confusion like this for similar issues.