Add some Windows Firewall netsh commands, some TFTP commands, and fix up issue #8

Added some Windows Firewall netsh commands whilst I was looking at adding some other information, think they don't belong in that section and would be more useful here. 

I've also added some TFTP persistance commands for uploading and downloading files. Simple stuff, but thought it would make the guide more complete.

The final commit should finish up the code for issue #8 

Let me know what you think :)