View BasicParticleSystem Frames in Jupyter Notebooks

[cesarr]

Added the BasicParticleSystem.writeParticlesNumPyText() method which serializes the coordinates of the particles in NumPy text format. The NumPy text files can be read from a Jupyter notebook to instantiate NumPy arrays that can be used to visualize the particles in the notebook using the K3D library (https://github.com/K3D-tools/K3D-jupyter).

[sebbas]

Thanks for the patch! I wouldn't be opposed to adding the Numpy text export function - it's seems simple enough to be added along the other export options.

The new code in /scenes is not generic enough to be considered for the main repository. scenes should only include Python files that showcase some of the core functionality (e.g. a new scene could be added if there is a new plugin).

All in all, this PR would have to be updated first as there have been some bigger changes to the file IO.