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resources has been revoked by the registrant of the domain.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

Add FILE_LICENCE declarations to almost all files that make up the
various standard builds of gPXE.

Add the concept of an abstract configuration setting, comprising a (DHCP)
tag value and an associated byte sequence.

Add the concept of a settings namespace.

Add functions for extracting string, IPv4 address, and signed and
unsigned integer values from configuration settings (analogous to
dhcp_snprintf(), dhcp_ipv4_option(), etc.).

Update functions for parsing and formatting named/typed options to work
with new settings API.

Update NVO commands and config UI to use new settings API.