MDL-47453 plagiarism: Add submission precheck for plagiarism plugins

Signed-off-by: Tony Butler <tonyjbutler@gmail.com>
MDL-47453 mod_assign: Precheck submissions against plagiarism plugins

Signed-off-by: Tony Butler <tonyjbutler@gmail.com>
MDL-47453 mod_forum: Precheck posts against plagiarism plugins

Signed-off-by: Tony Butler <tonyjbutler@gmail.com>
MDL-47453 mod_workshop: Precheck submissions against plagiarism plugins

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