Fixed 3D rendering mesh problem

main.cpp: Disabled color array (OpenGL Client State) that was causing the program to crash if no color vertex was sent with no lighting

wall.hpp: Changed the color of one type of wall (orientation)

model.hpp: Added normals to a model. Right now, the normals are (miss)calculated based on each triangle, so it doesn't head any normal data. Changed the draw method to draw only once after setting all the data up instead of calling a draw method to each triangle. That was awful for performance and was resulting on some glitches mentioned on last commit

models/teapot.obj: the famous GLUT teapot model