Refactor, bgfx integration

[stojanov]

Here we would hold the integration for the bgfx library for rendering.

This would also be the place to hold some restructuring and/or refactoring of some components to provide a better layout.

Planned stuff:

• [x] Event system rework a bit
• [ ] Renderer api rework
• [ ] Integrate bgfx
• [ ] Multiple window support

Still not finished, will work on this

[stojanov]

55% of what i implemented isn't useful, will refactor again, possibly add joystick/gamepad support