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Remove two scripts that are superceded by the Django admin interface
Remove dump-database.sh, which is misleading

dump-database.sh was only really useful for creating database
dumps that could be diffed, but people might think that it's
actually useful for backing up the database.  It's probably
best to just remove it.
Add two missing __init__.py files