[Icons] [MonoDevelop.Ide] New Windows icons:

* open
* save
* save-all

See https://github.com/xamarin/icons/issues/65

Signed-off-by: Vaclav Vancura <vaclav@vancura.org>
md-addins bump

Signed-off-by: Vaclav Vancura <vaclav@vancura.org>