Sg io

Several changes.
It fixes a bug where we forgot to add 'readwrite=False' to the device constructor and thus commands
start failing with an exception when they pass this argument :-(

Then there is a patch that adds a new linux_sgio directory and module. This is the same module as the builtin sgio module  but I break it out here so that it will be easier to package this separately.
(non-linux systems do not have a SG_IO module, they have other system specific interfaces,  so it is best to
move this out of pyscsi itself so that pyscsi can be used on non-linux platforms)

One patch removes the old sgio/sgiomodule.c module since we are by that stage already switched over to linux_sgio module.

Finally I rename the 'sgio' directory that now contains all of python-scsi and rename it to pyscsi instead.
I think this is a better name than the linux specific sgio name.


This now means that the main python-scsi module is no longer tied to linux, but will be possible to use on any system, (as long as they provide their own linux_sgio equivalent).

Portability YEY!