Job conf - we should not set gravity handlers for jobs/workflows before we set the job config

Reported by @torfinnnome We setup

```
+ handlers:
+ handler:
+ processes: 2
+ pools:
+ - job-handlers
+ - workflow-schedulers
```

pretty early in the tutorial, before we actually need job handlers. As a result it is possible to see an error message for

> dynamic handlers are configured in gravity, but galaxy is not configured to assign jobs to handlers dynamically

We should move the handlers setup down to the section on job configuration, it's probably a better time to discuss this topic as well

Find the tutorial section containing the shown handlers configuration and the later job-configuration section. Move the handlers setup and its explanation to the job-configuration section; done means the early tutorial no longer triggers the dynamic-handlers error before job configuration is introduced.

Written by the indexing model from the issue text.