TortoiseGitMerge: Implement smart tab

Signed-off-by: Sup Yut Sum <ch3cooli@gmail.com>
TortoiseGitMerge: Add Use spaces and Smart tab char buttons

Signed-off-by: Sup Yut Sum <ch3cooli@gmail.com>
Update Tortoise.pot

Signed-off-by: Sup Yut Sum <ch3cooli@gmail.com>