Negated ports

[theodore-norvell]

It should be possible to negate ports. A negated port will be drawn with a hollow circle. Here is an Or-gate with one port negated. (Bounding box is shown in green.)

[theodore-norvell]

In order to negate ports, we need to be able to select ports.

[theodore-norvell]

If we do this, then the only difference between the or and the nor component kind classes is how they initialize their output port. In fact, it makes me question whether there is value in having component kind classes for nand and nor. We can save room on the sidebar by not having them.