Add some installation and configuration notes for gitweb in
gitweb/INSTALL. Make use of filling gitweb configuration by
Makefile.
It does not cover (yet?) all the configuration variables and
options.
Some of contents duplicates information in gitweb/README file
(it is referred from gitweb/INSTALL).
Signed-off-by: Jakub Narebski <jnareb@gmail.com>
Signed-off-by: Junio C Hamano <junkio@cox.net>