format-patch: add --no-cc, --no-to, and --no-add-headers

These new options allow users to override their config settings for
format.cc, format.to and format.headers respectively. These options
only make git ignore the config settings and any previous command line
options, so you'll still have to add more command line options to add
extra headers. For example,

$ cat .git/config
[format]
to = Someone <someone@out.there>
$ git format-patch -1 --no-to --to="Someone Else <else@out.there>"

would format a patch addressed to "Someone Else" and not "Someone".

Signed-off-by: Stephen Boyd <bebarino@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>