Improved error handling, use new fileuploader
Improved error handling, use new fileuploader

The upgraded fileuploader returns a slightly different JSON response so
changed code to read from correct parameter.

Also added valid file extensions and an error message handler that will
add/use existing formError element to show information about invalid
file extension instead of uploading it happily.

leonidas/qa-reports,leonidas/qa-reports,leonidas/qa-reports