- Move ConnectorFactory to element-connector
- Introduce EndpointFactory for abstracting out the strategy for 
instantiating endpoints
- Expose a ManagedServer's endpoints by means of a
ServerEndpointRegistry
- JavaDoc improvements
- Add accessors for a server's endpoints to ServerInterface
- Make start() method of Endpoint throw an IOException if it cannot
be started
Add a property name constant for the default secure CoAP port to
NetworkConfigDefaults
Add test cases for retrieving endpoints from managed server