i18n: add--interactive: mark edit_hunk_manually message for translation

i18n: add--interactive: mark edit_hunk_manually message for translation

Mark message of edit_hunk_manually displayed in the editing file when
user chooses 'e' option.  The message had to be unfolded to allow
translation of the $participle verb.

Some messages end up being exactly the same for some use cases, but
left it for easier change in the future, e.g., wanting to change wording
of one particular use case.

The comment character is now used according to the git configuration
core.commentchar.

Signed-off-by: Vasco Almeida <vascomalmeida@sapo.pt>
Signed-off-by: Junio C Hamano <gitster@pobox.com>