Option to never show the tab list for a docker

[Lokasenna]

Seems simple enough.

I've got a docker set up on the left side of my screen for the track manager, region manager, etc, with a toolbar at the top to switch the view. I have absolutely no use for the little tabs, so it would be great to free up that space.

Ideally you could set this separately for each docker, although I'd personally be just as happy with a global On/Off setting.