[PBI] Notify application about registry change types

[p-schuler]

When applications are subscribing to registry changes, we want to indicate the type of change:

A new registration of a capability previously not available: added
An existing capability registration is removed: removed
An existing capability is modified (intents for example): modified

The type of modification is indicated in the event.

Consider the changes to be numeric represenations: 1 (added), 2 (removed), 3 (modified)

This depends on issue #8.

Acceptance Criteria

• The notification says what changed about the namespace, e.g. added or removed.

[stepknees]

Good feature to have, allows subscribers to dynamically understand capability changes. #backlog #newfeature