Structure selection

I got some time to work on AiS. I added structure construction selection (simple button for now). It creates a temporary model following the mouse until the player right or left click.

A right click will deselect the structure and the classic cursor will come back and a left click will build the structure. 3D model placement seems ok. I still have tricky bugs with cursor position on map but that's not a big problem (i guess).

Say hello to the refinery structure placeholder. That's a work in progress, I'll add more details on this model later :