Refactoring of Windows.py. Renaming classes to Windows_v5, Windows_v6

The Windows classes have been renamed following the major version
of the Windows kernel.
Added support for Windows 2012 and 8
Increased the timeout for Windows installatiosn based on kernel 6

The old 6000 timeout is not enough for Windows 8. In the same
testing system, Windows 7 & 2012 were insalled within 6000,
while Windows 8 took around 8000.