Do not strip empty lines / trailing spaces from a commit message template

Do not strip empty lines / trailing spaces from a commit message template

Templates should be just that: A form that the user fills out, and forms
have blanks. If people are attached to not having extra whitespace in the
editor, they can simply clean up their templates.

Added test with editor adding even more whitespace.

Signed-off-by: Boris Faure <billiob@gmail.com>
Based-on-patch-by:Sebastian Schuberth <sschuberth@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>