Wiring Tool: allow setting Constant Values directly into Inputs

[Nebual]

Inputs can currently hold a value without being connected to anything. Lets add UX to the Wiring Tool so it can directly set values, making explicit Constant Value gates optional.

This can also be used by Tool cpanels, so wheels can have a default "Torque" set on creation, which is just a wire input away from being dynamically changable.