Adds circuit wires

[cryhot]

I added the following features:

• wires can be selected in the toolbelt and used to connect/disconnect entities
• new settings option: Limit Wires Length (on by default). When deactivated, one can move and connect entities even if it makes a wire longer than the max distance. Wires that are too long are indicated as shaded. This feature is helpful for rearranging your circuits without having to cut wires temporarily.

[teoxoy]

This looks great! Thanks for the PR!

There seems to be an issue with the box/hit detection?

https://user-images.githubusercontent.com/28601907/219900207-aae2e327-07f2-4e78-be6d-c29343d390c1.mp4

[cryhot]

I see what you mean. I used the entity selection_box attribute to detect connection points (see getWire_connection_box). It is smaller that a cell for some entities like inserters and power poles (and I'm not even talking about entities with multiple connection points).

On the other hand, getEntityAtPosition return entities based on the cell. This leads to a situation where if the cursor is on a cell of an entity but not inside any of the connection points bounding boxes, then it shows the entity as "not connectable".

I'm not sure if we want to make the connection point hitbox bigger, or if we want to make getEntityAtPosition consider the selection_box attribute.

[cryhot]

I fixed the hitbox problem. Also fixed the settings problem. Also added the following feature:

• wire switches from red to green when pressing R