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resources has been revoked by the registrant of the domain.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>

The hardware address is an intrinsic property of the hardware, while
the link-layer address can be changed at runtime.  This separation is
exposed via APIs such as PXE and EFI, but is currently elided by gPXE.

Expose the hardware and link-layer addresses as separate properties
within a net device.  Drivers should now fill in hw_addr, which will
be used to initialise ll_addr at the time of calling
register_netdev().

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