Implement indexes for scalability.

 - Table: plagiarism_programming        Column: cmid
 - Table: plagiarism_programming_cours  Column: course
 - Table: plagiarism_programming_reslt  Column: reportid, student1_id, student2_id
 - Table: plagiarism_programming_jplag  Column: submissionid
 - Table: plagiarism_programming_moss   Column: settingid
 - Table: plagiarism_programming_date   Columns: settingid, finished, scan_date
 - Table: plagiarism_programming_rpt    Columns: cmid, version, detector
   (Replace just cmid index with multi key)