Added PreviewTextInput event with WPF implementation.
Added text input sample.
WPF.FileDialogBackend: check if no file selected
Update WidgetEvents Sample

Previous version was a quick and dirty one, and not one I'd like to see as a Sample!
This one is better style and works properly as well!
Merge branch 'master' of github.com:mono/xwt into text-input
[WPF] Removed support for default text foreground, which was interfering with region foregrounds.
[WPF] Use PreviewTextDown/Up instead of normal TextDown/Up so that events such as [Up] key press are detected.
[MAC] Fix mouse events on ListView (+ implements GetAtRowPosition)
Merge pull request #328 from Strnadj/mactableview

[MAC] Fix mouse events on ListView (+ implements GetAtRowPosition)
Merge pull request #320 from lytico/WpfFileDlgBug140404

WPF.FileDialogBackend: bug if no file is selected
Merge pull request #324 from hwthomas/master

Update (and correct) WidgetEvents Sample
Merge pull request #326 from luiscubal/text-editor

XwtPlus.TextEditor-related changes
Offset dirtyRect in Canvas OnDraw to allow for CanvasBackend origin
[GTK] rename changed Gtk3 TreeModel interfaces to reduce XWT_GTK3 usage
[GTK] add toolkit (gtk2/3) specific extensions to reduce XWT_GTK3 usage
[GTK] move Gtk3 ISearchTextEntryBackend impl to a separate file
[GTK] add a custom Gtk.CellRenderer base with toolkit (gtk2/3) specific implementations
[GTK] revert dangerous try/catch block
[GTK] add a custom GtkViewPort base for CustomViewPort with toolkit (gtk2/3) specific implementations
CustomViewPort must be sealed because of the new adjustment properties for Gtk3
[GTK] add a custom GtkDrawingArea base for ImageBox with toolkit (gtk2/3) specific implementations