tvb-docs: Align new sphinx generated DOM with CSS

We need to fix tvb-documentation resulted package to behave as it did in prev versions.
If you download "tvb-documentation-site.zip" from https://jenkins.codemart.ro/view/TVB/job/TVB%20-%20Step1/
the left-side menu is missing, and possibly other CSS parts are not matched.
We could look for DOM changes that might affect now the CSS code to apply correctly.

To generate the site locally:
python build_step1.py
in the local python env pip install sphinx docutils
The previous version is available live here:
https://docs.thevirtualbrain.org/index.html