Added a bunch of Grok patterns for Cisco ASA firewall syslog messages.

* Confirmed to work:
  * ASA-6-106015
  * ASA-1-106021
  * ASA-4-106023
  * ASA-5-106100
  * ASA-6-110002
  * ASA-6-302010
  * ASA-6-302013
  * ASA-6-302014
  * ASA-6-302015
  * ASA-6-302016
  * ASA-6-302020
  * ASA-6-302021
  * ASA-3-313001
  * ASA-3-313004
  * ASA-4-313005
  * ASA-3-313008
  * ASA-4-402117
  * ASA-4-402119
  * ASA-4-419002
  * ASA-6-602303
  * ASA-6-602304
  * ASA-6-713172
  * ASA-4-733100
* Based on patterns found here(https://gist.github.com/dav3860/5345656) and documentation here(http://www.cisco.com/en/US/docs/security/asa/syslog-guide/logmsgs.html#wp4771036)
  * ASA-2-106001
  * ASA-2-106006
  * ASA-2-106007
  * ASA-2-106010
  * ASA-3-106014
  * ASA-4-419001
  * ASA-4-500004
  * ASA-6-305011
  * ASA-7-710001
  * ASA-7-710002
  * ASA-7-710003
  * ASA-7-710005
  * ASA-7-710006