Modified Y_Carriage_xDia8_LM10UU and Duct for better bridge support

Added a small chamfer to key areas to parts where I was having difficult to bridge due to small walls and place to stick the bridges extremities.

UPDATE 05/2018: The issues I have with the bridges are related to a bug of Simplify3D! But it stills a better way to print when you have those chamfers :D