Add a VertexData class

This class replaces the series of list in the model class and should be
used for model data storage
It can be expended with as many attributes as desired
Currently the buffers are not interleaved
They aren't properly used either, the OpenGL30VertexArray class needs
to be completed first
Signed-off-by: Aleksi Sapon <QcTechs@gmail.com>