Add a button to cycle through possible rail blocks

[mayant15]

The priority system in RailBlockFamily's getClosestMatch function picks any rotation of the block with the highest priority from the set of possible blocks. We could add a hotkey (say e) or add a feature to the wrench which rotates a placed track or replaces it with a block of lower priority, allowing players to manually choose which blocks they want to place.

One way to do it would be to just follow the getClosestMatch function and run it again, going lower than the track already placed.