Enhance "Download RelaxNG button" in Profiler

[anneferger]

• see in add support for uploading ODD to profiler #13
• ODD is converted to RelaxNG via API call, this takes long but no process is shown
  To do:
• show progress using progress animation
• when odd is changed, RNG needs to be in process and not be downloadable: otherwise, it looks like the rng you download is the equivalent of the ODD, but it's not since it is the old one an still loading