completion: add missing configuration variables

completion: add missing configuration variables

Quite a few configuration variables have been added since 226b343
(completion: add missing configuration variables to _git_config(),
2009-05-03). Add these variables to the Bash completion script.

Also remove the obsolete 'add.ignore-errors' and
'color.grep.external', as well as 'diff.renameLimit.', which never
existed and rename the misspelled 'sendemail.aliasesfiletype'.

Signed-off-by: Martin von Zweigbergk <martin.von.zweigbergk@gmail.com>
Acked-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>