Improved the lighting model

	modified:   dist/fragment.glsl
Moved most uniforms related to lighting here from the vertex shader
New lighting algorithm uses square of the distance to a point light
	modified:   dist/vertex.glsl
Only interpolating normals to send to the fragment shader now, and most lighting calculations are done per fragment.
New uniform names and new uniform for the model matrix
	modified:   src/Window.cpp
Accomodating new uniforms, and setting their values accordingly.
	modified:   src/Window.h
Just new uniform locations (GLint member variables)