Fix post date setting update.
Ensure there is still a valid course module in cron

plagiarism_turnitin_config isn't cleared out when course modules are deleted
Merge pull request #116 from sk-unikent/patch-1

Ensure there is still a valid course module in cron
Incorrect repository submission check on PP fixed.
Version and Docs updated.
Post dates not updated for future PP assignments.
Cron scores update in the Plagiarism plugin are now split by submission type.
Only update post dates for course modules that still exist (Thanks to Skylar Kelty).