scipipe/scipipe: v0.6.4: Imrpoved logging and usability on missing (temporary) output files

This release brings a number of improvements around logging. The changes include:

• By default writing logs to a file in addition to stdout
• Issuing warnings on missing (temporary) output files after a task is executed, with a back-off-and-try-again three times before failing with an error message. (Previously the workflow would hang silently unless debug output was on).