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

... from the catalog
The `brooklyn.catalog` section can contain a libraries array, each item pointing to an OSGi bundle where the code for the blueprint is hosted. Evey type from the blueprint will be searched for in the libraries first and then on the standard brooklyn classpath.
```
brooklyn.catalog:
  id: xxx
  version: 0.1
  libraries:
  - name: <osgi-bundle-symbolicName>
    version: <osgi-bundle-version>
    url: <path to the jar file>
```
`name`, `version` are optional. A shorthand when url is specified only is:
```
brooklyn.catalog:
  id: xxx
  version: 0.1
  libraries:
  - <path to the jar file>
```

It's possible to use name & version only, url only or all at the same time. If name & version are only specified, then the runtime will check if there's an already existing bundle added to the catalog matching the name, version. The recommended approach is to always include url (so name & version only might not be worth mentioning at all).