Added RenderingItem

-Added the struct RenderingItem that holds a texture, a rect and a
templated value.
-Added function RenderItem() in Renderer that renders a RenderingItem
-Reoved all SDL_Texture/SDL_Rect/Value for local/remote
caption/lives/balls/points so that they all just use RenderingItem.
-Removed force from pointr/lives/caption as these should always and only
be changed when the value has changed.
Added simple particle system

-Added struct Particle that holds position, size, speed, rate of decay,
    alpha value, texture an whether it is alive.
-All particles are added to a vecor and updated in Renderer::Update()
-The particles are renderer in Render() and for each iteration, the
alpha value of the Particle's texture is set to the alpha value held in
PArticle
-For now, particles don't have a separate texture, so local player Ball
textyre is used. The alpha mod of this texure is reset when all
Particles have been renderered.
-Particles are spawned using Renderer::GenerateParticles()
-The particle effect can be tested by pressing y