Better default node group normal input

By default, Blender seems to have a hidden property that tells it what kind of default node group input normal to have - say, for textures, or just a vector. However, this is confusing, hidden and can't be changed (and bonus: buggy in 2.8)

I suggest that radio buttons are added to improve this, setting the default normal type. Options would be "None", "Shader normal" and "Texture vector".

• When "None" is selected, you get to select default values on the inside, and set current values on the outside (like "vector" has in the above picture)
• When the other 2 are selected, the default values are greyed out and you don't get to set the vector's current values outside (like "normal" is above).
  The normals you get are what you usually get for shaders/textures respectively, taking into account present displacement or UV, for example.

You'd get the type selected based on what you plugged into, same way other inputs inherit defaults.