Fixes on the Research Tree

Hello there. Quite a moment since I talked about Alone in Space. I had hard days at work and no energy nor motivation to get back on code during nights.

But that's it! I worked tonight!

First, I made improvements on the tree rendering. I was wondering why the game was taking so much time to completely close before thinking about a memory leak. And there it was. I burnt this bug. Now everything is fine! :-)

I also corrected some placements in the tree viewport. Some nodes were rendering outside of the viewport zone.

Node now react on click. Clicking on a node center the viewport on the clicked node. Later, this will open the technology window as well. There will be a small drag animation instead of the current "teleportation".

This image shows debug zones in red. You can see the vertical line defining the tree viewport limit and the zone around the first node which is currently hovered. Nothing very fancy for now.

I still have zoom issues but I'll get rid of this soon (I guess).