Node editor - Cosmetic settings

Proposed change: Add three mostly cosmetic settings for the node editor.

1: 'Extend Wires' (Numerical Setting). This would add an offset to the beginning and end of wires, similar to Unity's shader graph. The length would be set by the user (including 0).

2: 'Expansion Direction' (Dropdown Menu). Currently, when you add a node in between two already-connected nodes, all of the nodes 'downstream' get pushed to the right. This would allow you to change the direction, or entirely disable the behaivour.

3: 'Auto-Frame Nodes' (Checkbox). If enabled, when you switch to a different material and no nodes are visible, the view will automatically shift to frame all nodes.