Help improvements

[box293]

The help should explain that Warning and Critical use the Nagios Plugin Threshold standards. I assume this is the case, the code doesn't have any comments and my Python knowledge isn't that great.

/usr/local/nagios/libexec/check_mssql_server.py --help
Usage: check_mssql_server.py -H hostname -U user -P password -T table --mode

xxxxxx

  Nagios Plugin Information:
    -w WARNING, --warning=WARNING
                        Specify warning range.
    -c CRITICAL, --critical=CRITICAL
                        Specify critical range.

Same appears for check_mssql_database.py.