Added mod_feature_user_stats module

This module create the following users_data entries...
mysql> select * from users_data;
+----+--------+-------------+-------------------------------------------------+--------------+
| ID | UserID | LastUpdated | Name                                            | Value        |
+----+--------+-------------+-------------------------------------------------+--------------+
| 26 |      1 |  1301181002 | mod_feature_user_stats/CurrentMonthTotalTraffic | 1            |
| 27 |      1 |  1301181002 | mod_feature_user_stats/CurrentMonthTotalUptime  | 244          |
| 28 |      1 |  1301181002 | mod_feature_user_stats/NAS-Identifier           | Neemo        |
| 29 |      1 |  1301181002 | mod_feature_user_stats/Framed-IP-Address        | 192.168.0.99 |
+----+--------+-------------+-------------------------------------------------+--------------+
4 rows in set (0.00 sec)

Added to config file

Fixed bug in config file regarding users_data query