Introducing VBO (Vertex Buffer Object) concept with a support of VAO (Vertex Array Object)

Introducing VBO (Vertex Buffer Object) concept with a support of VAO
(Vertex Array Object) referencing a different set of vertex attributes,
which can be stored in the same vertex buffer object or split across
several vertex buffer objects.
Currently only SkyBox and FileNodes (files, dirs, drives) are drawn
using this method.
VBOUtil is the main class supporting this concept.
To optimize further, use tips given on:

https://developer.apple.com/library/ios/documentation/3DDrawing/Conceptual/OpenGLES_ProgrammingGuide/TechniquesforWorkingwithVertexData/TechniquesforWorkingwithVertexData.html#//apple_ref/doc/uid/TP40008793-CH107-SW1