move the release mouse functionality into a separate function
initial DockBar widget

currently supports tab tearoff. does not yet support reattach.
stub out a hacky DockArea widget

the DockArea is the root manager widget
export the DockBar and DockArea
add the DockTab class
disable automatic tab creation in the dock bar
add first cut at DockItem class
variable naming, code ordering
add the first cut of a DockPanel
code ordering
fix typos
only export DockArea and DockItem in the public API
wip commit
rename dockbar -> tabbar within a DockPanel
unset the current tab before tearing it off
move push/pop cursor to tab mover
add a fixme comment
wip
have the user supply the dock item id
add a dockParent property to the DockPanel