send-email: --suppress-cc improvements

send-email: --suppress-cc improvements

Since 6564828 (git-send-email: Generalize auto-cc recipient
mechanism., 2007-12-25) we can suppress automatic Cc generation
separately for each of the possible address sources.  However,
--suppress-cc=sob suppressed both SOB lines and body (but not header)
Cc lines, contrary to the name.

Change --suppress-cc=sob to mean only SOB lines, and add separate
choices 'bodycc' (body Cc lines) and 'body' (both 'sob' and 'bodycc').
The option --no-signed-off-by-cc now acts like --suppress-cc=sob,
which is not backwards compatible but matches the name of the option.

Also update the documentation and add a few tests.

Original patch by me. Revised by Thomas Rast, who contributed the
documentation and test updates.

Signed-off-by: Jay Soffian <jaysoffian@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>