Scene Graph and Mesh Loader

This update brings lots of fun stuff.

As the title suggests a basic Scene Graph was added. Allowing the stacking of elements with much more ease.

A major component of the graph is the Actor, which acts as a node, including also an optional mesh and shader program.

Picking up on the mesh, a mesh loader was added, it currently only loads simple obj files, but I hope the improve it further. A Mesh is now the recommend class to use to define objects.

Additionally a couple of managers were added. ShaderProgramManager and MeshManager. Allowing the storage of said objects. Therefore Actors can share shaders and meshes with no problem.

Finally a Simulation was added. This class allows the execution of repeating updates. Just implement a IUpdatable class an add it to the Simulation.

See the latest example on how to use the refereed components correctly.