plagiarism_turnitin: Fix image references in style rules

Signed-off-by: Tony Butler <tonyjbutler@gmail.com>

Conflicts resolved:
	plagiarism/turnitin/styles.css
plagiarism_turnitin: Fix errors screen error caused by file absence.

Conflicts resolved:
	plagiarism/turnitin/turnitinplugin_view.class.php
plagiarism_turnitin: Only update grades if grading scheme is numeric

Signed-off-by: Tony Butler <tonyjbutler@gmail.com>

Conflicts resolved:
	plagiarism/turnitin/lib.php
mod_turnitintooltwo: Fix access to grademark and originality reports.

When quick grading is enabled, access to grademark and originality reports
was not possible because of form conflict.
plagiarism_turnitin: Include lib/gradelib.php for grade_update()

Signed-off-by: Tony Butler <tonyjbutler@gmail.com>
mod_turnitintooltwo: Check connection to TII before verifying EULA

Signed-off-by: Tony Butler <tonyjbutler@gmail.com>
mod_turnitintooltwo: Test TII API before checking for EULA acceptance

Signed-off-by: Tony Butler <tonyjbutler@gmail.com>
plagiarism_turnitin: Fix bugs in file submission error log code

Signed-off-by: Tony Butler <tonyjbutler@gmail.com>
plagiarism_turnitin: Fix bugs in due date / cut-off date logic

Signed-off-by: Tony Butler <tonyjbutler@gmail.com>