mc.py: bugfixes, improvements and code-cleanup
mc.py: bugfixes, improvements and code-cleanup

Changes to `mc.py`:
   **Bugfixes**:
         - fixed a bug in the dropbox setup where menu entries were swapped
         - fixed a bug preventing the troubleshooting help to be shown
   **Improvements**:
         - added hint about what to enter when asked for the `access_type` in the dropbox setup
   **cleanup**:
         - removed unused variable asignments
ywangd/stash,ywangd/stash,cclauss/stash,cclauss/stash