Support for adding YAML defined policies to the catalog.

Includes support for loading from OSGi bundles.

Example:

```yaml
name: Demo Policy
brooklyn.catalog:
  id: demo_policy
  version: 0.1.0
  libraries:
  - url: file:///<path>/mms-sample-policies-0.1.0-SNAPSHOT.jar
brooklyn.policies:
- type: io.cloudsoft.ibm.mms.amp.policies.CompliancePolicy
  brooklyn.config:
    period: 20s
```

<del>
The format is not in CAMP spec, just adhoc yaml, therefore feedback on the syntax is welcomed.
Sample yaml:

```yaml
name: Demo Policy
brooklyn.catalog:
  id: demo_policy
  version: 0.1.0
  libraries:
  - url: file://<path>/mms-sample-policies-0.1.0-SNAPSHOT.jar
policy: io.cloudsoft.ibm.mms.amp.policies.CompliancePolicy
```

If configuration in catalog is required (can be overriden when referenced in the app yaml):

```yaml
name: Demo Policy
brooklyn.catalog:
  id: demo_policy
  version: 0.1.0
  libraries:
  - url: file:///<path>/mms-sample-policies-0.1.0-SNAPSHOT.jar
policy:
  type: io.cloudsoft.ibm.mms.amp.policies.CompliancePolicy
  brooklyn.config:
    period: 20s
```

Analogous to config & catalog, perhaps I should prefix it with "brooklyn.".

</del>