TreeView work in progress...
Merge branch 'master' into treeview
Added some more tests.

Still don't show up the bug I'm looking for...
Fixed a binding bug.

StyleActivator wasn't signalling OnCompleted when it was subscribed in a
completed state, causing styles to be applied to controls that would
never activate.
Make default StackPanel orientation Vertical.
TreeView now displays stuff.
Added an expander on the tree view items.
Change the threshold for image comparisons.
Added a Path test.
Added the test expected output.
Added TreeViewItem.IsExpanded.
Merge branch 'master' into treeview
Merge branch 'master' into treeview
Align treeview node expanders properly.
More work on TreeView.
Fixed failing test.
Implemented two-way binding.

And hooked up the TreeViewItem's expander button. The hit testing on it
is a bit off though...
Fixed click and grandchild display.
Added opacity.
Added classes to debug output.