Changes to SceneNode, Shader, Mesh, Entity

Entity----
Now render is inherited from movableObject.
Mesh----
Added location of vertexPosition from shader enum to the
vertexattribpointer
MovableObject----
Created a pure virtual function, render(glm::mat4).
SceneNode----
Now constructors asks for a pointer to the current SceneManager.
Added function processRootSceneNode().
Added a pointer to the current SceneManager.
Added functions processChilds and processObjects.