Aviation and FX update

Hello!

This update includes a lot of new bricks, features and bug fixes! Some of the changes:

• Added wings, propellers and thrusters
• New machine gun
• Large gun now shoots explosive rounds
• New explosion particle and sound effects
• Fixed an occasional crash with colliding bricks
• New brick materials (colors) and proper material vizualization in the editor

Note: Since this update features a lot of changes (including an update to the new Unreal Engine version) new bugs are to be expected and thus it is only available in the Beta branch for now.