Resolve "Update documentation on virtual env. for Alpha"

• fixed example for pytorch/torchvision in venv
• add workspace creation for venv in example
• add hint for workspaces and venv in general
• quick fix for deprecated JH section

Closes #533 (closed)

doc.zih.tu-dresden.de/docs/jobs_and_resources/alpha_centauri.md

@@ -172,10 +172,10 @@ additional Python packages and create an isolated runtime environment. We recomm
 ### JupyterHub
 
 [JupyterHub](../access/jupyterhub.md) can be used to run Jupyter notebooks on Alpha Centauri
-sub-cluster. As a starting configuration, a "GPU (NVIDIA Ampere A100)" preset can be used
-in the advanced form. In order to use latest software, it is recommended to choose
-`fosscuda-2020b` as a standard environment. Already installed modules from `modenv/hiera`
-can be preloaded in "Preload modules (modules load):" field.
+cluster. You can either use the
+[standard profiles for Alpha](../access/jupyterhub.md/#standard-profiles) or use the advanced form 
+and define the resources for your JupyterHub job. The "Alpha GPU (NVIDIA Ampere A100)" Preset 
+is a good starting configuration.
 
 ### Containers