Access to the gpxe.org and etherboot.org domains and associated
resources has been revoked by the registrant of the domain.  Work
around this problem by renaming project from gPXE to iPXE, and
updating URLs to match.

Also update README, LOG and COPYRIGHTS to remove obsolete information.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

Signed-off-by: Michael Brown <mcb30@etherboot.org>

These commands can be used to activate or deactivate the PXE API (on a
specifiable network interface).

This is currently of limited use, since most image formats will call
shutdown() before booting the image, meaning that the underlying net
device gets shut down during remove_devices() anyway.