Added support for Cisco ASA Connection graphs

This will create graphs within the firewall tab for Cisco ASA firewalls.

Example:

http://snag.gy/9Qx9C.jpg

Code is written so that for Cisco ASA we can add additional snmp queries in the file and store results in the database. The new table has support for high / low limits along with disabled for the ability to do alerts in the future.