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resources has been revoked by the registrant of the domain.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 SRP Boot Firmware Table serves a similar role to the iSCSI and AoE
Boot Firmware Tables; it provides information required by the loaded
OS in order to establish a connection back to the SRP boot device.