Generate heading event on DM4 import

Previously the heading information was on bookmark event, but now we
trigger a heading event when direction info is available.

Signed-off-by: Miika Turkia <miika.turkia@gmail.com>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Manually add bookmarks in the profile context menu

Use the infrastructure created for manually adding gas change events to
also be able to add bookmarks.

[Dirk Hohndel: This combines two commits for clarity. I also cleaned up
               the indentation and changed the code to no longer print the
               exact same text twice.]

Signed-off-by: Robert C. Helling <helling@atdotde.de>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>