Improve documentation on install process for features such as OpenVR and Jupyter

[cyanpelican]

Here are my notes:

To install as a jupyterlab kernel (after building for your OS):

1. Install jupyterlab: pip install jupyterlab
2. Install kernelspec: cd install; python3 -m Pluto.install
3. Install ipywidgets: pip install ipywidgets

To install OpenVR compatibility

1. Clone the openvr repo to ~/OpenVR
2. Pass -DBUILD_OPENVR=ON -DOPENVR_SDK=~/openvr to cmake on the configure step

• (cmake -G "Visual Studio 15 2017 Win64" -DBUILD_OPENVR=ON -DOPENVR_SDK=~/libs/openvr -DCMAKE_BUILD_TYPE=Release ../)