Implemented usage of `Camera` object:
    * Makes it easier to track player
    * Camera boundary used for culling off-screen sprites

Created visual representation of Player hitbox and ground area, as well
as Quadtree node structure.
separated code for starting server and starting client from init body
Added quadtree injection of all physics components in main loop.
Added `active sprites` counter to debug info.
changes player init code to use emplace instead of assignment
added comments for easier reading.