Top command ribbon can tear away

[Tristan Croll]

It turns out that the lovely new tabbed ribbon at the top of the ChimeraX window has a *tiny* area where clicking and dragging will pick it up and tear it out into a floating widget. I just managed to do it completely by accident, and even knowing that there is a "pick up and drag target" there *somewhere* it's nearly impossible to find it to dock it back in place. I think it would be better to make this widget explicitly non-floatable?

[pett]

You can also do this by unchecking "Dockable Tool" in the context menu, and this problem also applies to any tool without a toolbar (e.g. Command Line).

The plan here, rather than make such tools perma-docked, is to add a title bar when they are undocked and remove it when they are docked.

[pett]

Added explicit option to allow tool windows to suppress their title bars, and based on that setting hide/show the title bar when the tool is docked/undocked.