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resources has been revoked by the registrant of the domain.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

Exclude proto/uip, since uip.c and uip_arp.c both have global variables
called "c", which screws up doxygen's auto-generation of links to file
documentation when it encounters a file name such as "hello.c".