Fixed the compilation error in Math library

Spelling mistake in the for loop fixed.
Renamed the shaders

The shaders will be used for rendering ambient light.
Shaders are now singletons

Shaders have been made singletons to prevent from rebuilding the same
shader program over and over again.
Forward rendering- ambient light introduced.

Ambient light introduced in the forward rendering technique.
Renamed the shaders.

Renamed two shaders. For now they are not useful. Rendering engine setup
is ready to perform other lighting calculations.
Forward rendering. Directional lights

Forward rendering. Multipass rendering extended with directional lights.
Introduced a new vertex and fragment shader.