Teach "-m <msg>" and "-F <file>" to "git notes edit"

Teach "-m <msg>" and "-F <file>" to "git notes edit"

The "-m" and "-F" options are already the established method
(in both git-commit and git-tag) to specify a commit/tag message
without invoking the editor. This patch teaches "git notes edit"
to respect the same options for specifying a notes message without
invoking the editor.

Multiple "-m" and/or "-F" options are concatenated as separate
paragraphs.

The patch also updates the "git notes" documentation and adds
selftests for the new functionality. Unfortunately, the added
selftests include a couple of lines with trailing whitespace
(without these the test will fail). This may cause git to warn
about "whitespace errors".

This patch has been improved by the following contributions:
- Thomas Rast: fix trailing whitespace in t3301

Signed-off-by: Johan Herland <johan@herland.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>