Replace two old scripts with Django admin commands

Instead of:

  ./insert-example-projects.py

... you would run:

  ./manage.py catmaid_insert_example_projects --user=1

And instead of:

  ./setup-tracing-for-project.py 3 1

... you would run:

  ./manage.py catmaid_setup_tracing_for_project --project=3 --user=1

This also has the advantage that you don't need to put your
database details redundantly in ~/.catmaid-db
Remove two scripts that are superceded by the Django admin interface