plagiarism_turnitin: Release feedback based on marking workflow state

Signed-off-by: Tony Butler <tonyjbutler@gmail.com>
plagiarism_turnitin: Truncate uploaded file names to <= 100 characters

Signed-off-by: Tony Butler <tonyjbutler@gmail.com>
plagiarism_turnitin: Always allow all file types to be accepted by TII

Any restriction of file types will now be taken care of by the Moodle
file upload assignment submission sub-plugin.
plagiarism_turnitin: Remove non-ASCII characters from file name
plagiarism_turnitin: Reduce max file size for TII submissions to 20 MB