Updated Graphics, ParticleSystem and World

[brenobaptista]

• graphics.setBackgroundColor was missing the table argument
• pSystem:setSizes had to use optional parameters
• pSystem:setColors had to use optional parameters and was missing the optional table arguments
• world:setCallbacks had to use optional parameter

Technically, we also need to update the particle system to include all the missing optional arguments (a1, a2, a3, a4, a5, a6, a7, a8) instead of just (a1, a2, a8).

I got a little confused on the pSystem:setColors method, can somebody double check it?

[MikuAuahDark]

ParticleSystem:setSizes and ParticleSystem:setColors interpolates up to 8 different sizes and colors, if you specify that much.