[Feature request] App settings

[keptsecret]

Implement AppSettings class that will read from an .ini file on startup and store the settings inside the class variables.
Make value access static, so we can call AppSetting::FOV.

Need following values used as setting for now:

• screen resolution
• fullscreen or windowed
• fov
• mouse sensitivity

First two values are used in the initialize() of the Application class to create the GLFW window. The other two are used in camera constructor. The .ini file can be read/edited as a normal text file, so it can just look like:

screensize:
    width: 1920
    height: 1080
fullscreen: 0
fov: 90
mousespeed: 5

(0/1 for booleans)

[keptsecret]

Worked on by #69