Updated ParticleSystem.cpp and InitShader.cpp

Refactored addSomeParticles() to updateNumParticles.  Takes an int, N,
and adds or removes N particles from the particle vector.

Made a fix to InitShader where a GL_ERROR was being produced.

Made addParticle(), removeParticle(), and setNumParticles() private.
updateNumParticles() is now the default method of changing the number
of particles.
Merge branch 'master' of https://github.com/UMLComputerGraphics/GraphicsProject