Blender Git Loki

Fix T68702: Input socket in the Normal node isn't drawn properly.

The Normal vector socket in the Normal node wasn't drawn properly and
couldn't be controlled. Additionally, the socket name was drawn over it.

This happened because the socket had a default value of a zero vector.
To fix this, we set the default value to the unit vector `(0, 0, 1)`.
Moreover, we don't draw the UI name if the subtype is `PROP_DIRECTION`.

Reviewers: brecht

Differential Revision: https://developer.blender.org/D5503