update docs for nT datastructure(s)

Created by: jorana

What is the problem / what does the code in this PR do Currently only TPC plugins are displayed in the data-structure, furthermore these are only displaying the 1T datastructure.

With these changes we expand the documentation to show the HE and NV data-structure

How to implement Currently we only build the documentation on the stable and master branch. Hence to allow for an effective PR-review process I propose to merge this PR with only a very minor review and fine tune the result based thereon as we would be able to see the result and improve from there (if needed).