[v0.5.0] Smelting, forging and aerodynamics

 -Hematite (can be smelted into iron)
 -Forging system
 -Drag and lift force
 -Big Red Slime
 -Added a camera monitor in the menu window
 -Made hot objects emit light
 -Improved rendering performance
 -Material parameter adjustment
 -Disabled day-night cycle by default
 -Fixed a bug that the window could not be opened with Index Controller
 -Fixed an issue where maximum speed cannot be achieved with VIVE Controller
 -Other minor fixes