Fix #224. Handle correctly recovery protocol

For the attribute `channelIDs` sent on `hello` message:

1. If channelIDs is `undefined` or `null` --> it ignores the attribute
2. If channelIDs is an empty array --> it clears all registration for the node
3. For each element on `channelIDs`:
 * If the element is on the registered apps for the given node: do nothing
 * If the element is not on the registered apps for the given node: unregister it
 * If there are pending elements on the `channelIDs` array, register them (with the registration message)