- refactored scene_main to be able to share code between software and
  hardware renderers, while still sharing code between terminal software
  renderer and graphical software renderer
- made the hardware renderer use scene objects vertices and transforms,
  instead of hardcoded ones
- made the hardware renderer use the scene's camera
- made .obj parser create Vector3 instead of Vector4, which didn't made
  sense
- removed unnecessary std::
- lots of small changes

- fixed aspect ratio being the inverse of what it's supposed to be
- use std::chrono::high_resolution_clock instead of system_clock
- convert ellapsed time to float representing seconds
- renamed engine::math::Matrix4::projection to perspective
- use [0,1] instead of [-1,1] for the range of z values, to be aligned
  with vulkan
- added engine::math::Matrix4::{look_at,transpose}