Support flip for tile item

[jDomantas]

Rotating a blueprint with hazard concrete changes its rotation expected, but flipping it does nothing at all. I would expect it to change to the other orientation.

[boskid]

I could implement this abusing the assumption that the rotate of the hazard concrete makes it look as after the flip, but that would be not fair for the implemented logic of TilePrototype as they have a next_direction defined. I can easily think of a case where a mod would create a 4 directional tile (lets simply go with an arrow) where a vertical arrow should not flip horizontally while the vertical arrow would flip to the opposite when doing a vertical flip. That means that to have this properly fixed i would have to add more fields to a TilePrototype like flippedHorizontal and flippedVertical id connectors so the flipping would handle properly those extra cases. Then there would be a possibility that a mod would create a tile which is not affected by a rotate but is affected by a flipping (like a left swirl turning into right swirl) making a regular terrain building to also require a flip handling as otherwise it would only be supported by a blueprint building.

For now i am considering this to be a minor issue but maybe other dev would want to implement this so i am leaving this topic where it is.