[WPF] TreeView fixed wrong Shift selecting + implemented Keyboard support
Add support for multi-line text entries
Merge pull request #210 from DavidKarlas/wpfTreeView

[WPF] TreeView fixed wrong Shift selecting + implemented Keyboard support
[Mac] Fix selection events in ListBox
Reuse event IDs from ListView in ListBox
[Mac] Updated reference test images
Fix some unit tests
[Mac] Fix radio button tests
Handle font size properly on Mac
Add ScrollAdjustment property to Scrollbar
Make Scrollbar.ScrollAdjustment public
[WPF] Fix build by adding missing interface property
[Mac] Fix size calculation issue for custom widgets

Custom widgets with content have to get their size from
the content.
Round widget coordinates when placing widgets

In toolkits like Cocoa, placing widgets on non-integer coordinates
makes the widget look blurry.
[Mac] Honor borderless style in Button
Initial work to move align and expand properties to the Widget class
Initial work to simplify the size negotiation model

Instead of having GetPreferredWidth/Height pairs
we now have a single GetPreferredSize method
which can take constraints as parameter.
Honor the positioning Rectangle passed to Popover.Show

If the passed rectangle is Rectangle.Zero, it defaults to the screen bounds of the reference Widget.
Otherwise, it represents an area inside the reference Widget relative to which the popover will be shown.
Ongoing work to simplify de size negotiation model

Done the required changes in the GTK backend.
Api adjustments.
[Mac] Track api changes in size negotiation model