Adding lights for Christmas!

Changelog

Getting ready for Christmas! And getting ready for going physically based, really.

• Added simple light component classes (directional).
• Added example code on the dev example.
• Added default materials Unlit, Screen, and Standard.
  • Standard will eventually become a physically based material. At the moment, it is Phong lit.
• Refactored all shader code.
  • Added common shaders for shared features.
  • Now the user doesn't need to:
    • Add #version 330 tag.
    • Define position, normals and uv vertex attributes in the shader. Getters in the format of getPosition() are provided for its use.
    • Define default varying data for the fragment shader. However, if the user wants to use the data in the shader, they can call several different functions to setup the data (setupWorldSpaceOutput(), setupScreenSpaceOutput()) or setup each of the values separately (setupPositionOutput(), setupNormalOutput(vec3())).
    • Define the Common uniform block. Every shader will have access to its variables. Also, some helper functions have been provided for the user such as getClipPosition().
    • Define texture uniforms. They can be accessed with u_tex0, u_tex1, u_tex2...
    • Define out fragColor. Output color can be set using setFragmentColor(vec3 / vec4).
  • Some helper functions such as computeLightContribution() have been added. At the moment, not much functionality is available, but soon a lot of other functions will follow!
• The editor now has an option to be hidden and show the application full-screen.
• Shaders are no longer located in the assets folder. Now they are inside of each backend folder inside of src/graphics.