Improve error-logging for pdfconverter

To make servicedesk requests easier regarding maintaining the visual, the errors logged in the container should be accessible within T5. Also, the log should be accessible throughout the lifetime of the task and no persistent data should stay in the container

• Add endpoint to pdfconverter that retrieves the logs for a Job (merged to a single chunk) and purges all data for the job
• Save this log as "pdfconverter.log" in the task-data /visualReview/log Dir (for every job, also those, that worked without error). This dir can be added as a class-constant in the plugin-init, is not neccessary to have that configurable
• In case of Exception 'E1186' add the log-data to the Event
• Instead of the $maxTries = 100; in the work-method the editor_Plugins_VisualReview_PdfToHtmlWorker class should have a constant with the max time in minutes we wait for the Job to complete. For now we should use 30 min (now we have 500 sec, what is too short from my experience)
• The "docker logs pdfconverter" command gives all the GET-requests out of the request-loop. It would be better to have just the post-requests logged if possible