use mysqli for escaping input string. fix some errors logged to system.log

mysql_real_escape_string is deprecated, use mysqli instead.

Also fix what was causing these entries in system.log:
2014-02-26T12:24:48+00:00 ERR (3): Notice: Undefined index: port  in /home/kguest/bin/Wiz/app/plugins/Sql.php on line 62
2014-02-26T12:25:17+00:00 ERR (3): Notice: Undefined index: port  in /home/kguest/bin/Wiz/app/plugins/Sql.php on line 51
2014-02-26T12:46:40+00:00 ERR (3): Notice: Undefined variable: batch  in /home/kguest/bin/Wiz/app/plugins/Sql.php on line 86