Improve batch processing of large pre-existing datasets

[jkva]

This issue is related to #95. Ideally we can use a regular AJAX-based mechanism without relying on external proxy-processors as we do right now using the remote NodeJS-based post processor.

Apart from that, the settings page should:

• show whether a processing task is currently running;
  • if so: allow cancellation of the current running task
  • show when this job was started;
  • show the current progress (percentage, processed n posts of total)
• when the task is finished, show an overview (processed n posts in m minutes)
• allow the starting of a task (when a valid API profile exists)