Bugfix: Cam Shake

There is no cam shake! But it was looking like it when FPS went low. Issue was that I use _delta*20.0 as ratio in a lerp and in low frame this can grow > 1.0. Now it do min(1.0, _delta*20.0) and it's fine!

Bugfix: Doubled UI

Sometimes there could be several UIs open even though only 1 should be shown. I guess the reason was, that XP boxes send an "unregister UI"-command even though they didn't open a UI. I hope this was the issue.

Bugfix: Engines didn't hurt Ghosts

Now the engines can hurt ghosts. Necessary for Scout ship.