implement Scaffold for Database Management
fix belongTo bug when
        $this->belongsTo("coach_id", "Account", "id");
        $this->belongsTo("student_id", "Account", "id");
coach_id would be discard
Merge pull request #51 from wenchen/2caea51b07fe820f079ebc861f834c1d7f1a4c23

 fix belongTo bug