Delete all data records in a model, obeying `clear`, `dry_run`, and `verbosity` flags
    
    If a clear was requested (dry_run or otherwise), return the number of records deleted (# before minus # after)

def clear_model(model, dry_run=True, verbosity=1):
    '''Delete all data records in a model, obeying `clear`, `dry_run`, and `verbosity` flags
    
    If a clear was requested (dry_run or otherwise), return the number of records deleted (# before minus # after)
    '''
    N_existing = model.objects.count()
    if dry_run:
        print "DRY_RUN: NOT deleting %d records in %r." % (model.objects.all().count(), model)
    if N_existing:
        ans = 'y'
        if verbosity and not dry_run:
            ans = raw_input('Are you sure you want to delete all %d existing database records in %r? (y/n) ' % (N_existing, model))
        if ans.lower().startswith('y') and not dry_run:
            model.objects.all().delete()
        return N_existing - model.objects.count()
    return 0