Adds basic instructions for adding blueprints to and removing blueprints...

... from the catalog
Also possible to add policies to the catalog, sample yaml:

```
brooklyn.policies:
- type: brooklyn.osgi.tests.SimplePolicy

brooklyn.catalog:
  id: simple-policy
  version: 1.0
  # see OsgiTestResources
  libraries:
  - classpath:/brooklyn/osgi/brooklyn-test-osgi-entities.jar
```