Add SQL-KPI data source which will show DC leaderboard with Last Month position and relative place

So the line should look like:

| Position_this_month | member_name | member_points_this_month | lastmonth_position | member_position_lastmonth_delta |
|---------|------------------------|-----------|----------------|--------------|
| 1 | member100 | 1000 | 23 | +23 |
| 2 | member1 | 990 | 1 | -1 |