Handle missing docutils in CLI

Handle this error when not required:

Traceback (most recent call last):
  File "/home/armarx/code/armarx/ArmarXCore/build/bin/armarx", line 27, in <module>
    import armarx_cli.armarx_control
  File "/home/armarx/code/armarx/ArmarXCore/etc/python/armarx_cli/armarx_control.py", line 25, in <module>
    from .commands import *
  File "/home/armarx/code/armarx/ArmarXCore/etc/python/armarx_cli/commands/List.py", line 21, in <module>
    from docutils.nodes import topic
ModuleNotFoundError: No module named 'docutils'

Follow-up (but takes more work): Let armarx CLI use its own virtual environment.