change VertexBuffer to store definition of vertex attributes in
VertexDescriptors
fix error in Vector3F.getSquaredLength()
add method Vector3F.normalize()
add method Matrix4F.loadFrustum(...)
add method Matrix4F.loadOrhto(...)
add method Matrix4F.loadView(...)
change types Float3 to Vector3F, float[] to Matrix4F
add javadoc for class VertexDescriptor
change Uniform.M4f to extend Uniform<Matrix4F>
change Uniform.M3f to extend Uniform<Matrix3F>
fix calculation of attribute offsets in VertexDescriptor
add method VertexDescriptor.hasAttribute(VertexAttribute)
add method Uniform.setValue(T value)
add javadoc
add preDraw, postDraw calls