The color picker button is a simple button, which lets the user pick a color. It opens a SelectColorDialog and displays the selected color when finished.
This PR contains a ColorPicker XWT implementation with a default Xwt based backend, which is used if the active backend lacks IColorPickerBackend implementation. The default backend mimics GtkColorButton (https://developer.gnome.org/gtk2/2.24/GtkColorButton.html).
A native Gtk IColorPickerBackend implementation is included, too.
add ColorPicker button with a default xwt based backend
[GTK] add color picker backend
Merge remote-tracking branch 'mono/master' into add-color-picker
Merged with some conflict fixes and a native mac implementation.