decide on a new graphics api #251

OpenGL is a dead end on macOS.

Possible choices:

• Use Vulkan if macOS does not need to be supported.
• Use Vulkan for windows/linux, and use metal for macos.
• Use WGPU (cross platform but no gpu ray tracing or other bleeding edge features)
• Use Vulkan and MoltenVK for mac.
• Use a third party graphics abstraction layer that can be plugged in to a Qt window, that allows totally custom shaders