#663 [Feature] Tab move on drop instead of drag

[Reina Sweet]

This adds a new preference that allows tabs to be moved only on release instead of middle move. Effectively, this makes drag and drop with multiline tabs actually usable.

Details:
This option defaults to off and is in Settings -> Preferences... -> General within the Tab Bar section.
While on, this option changes the behavior of dragging and dropping tabs. Dragging a candidate tab no longer moves tabs as you drag. Instead, a solid bar is drawn in the area the tab would be dropped into if the user releases the mouse button. Upon releasing the tab is dropped in the area specified by the bar.