got rid of XML intermediate step (we now depend on tabula-extractor gem)
lots of cleaning still to do
Merge remote-tracking branch 'origin/background_job_wrapper' into background_job_wrapper

Conflicts:
	lib/jobs/generate_thumbnails.rb
	tabula_job_executor/jruby_executor_service.rb
	tabula_job_progress.rb
	tabula_web.rb