Changes

Remove suppressWarning("deprecation")

Too many "deprecation" will be hidden, we should probably live with some
warning about backward compatibility.

#933: Add new interfaces to core: Destroyable, Startable and Stoppable

Signed-off-by: moznion <moznion@gmail.com>

#933: Mark as deprecated for server.(Destroyable, Startable, Stoppable)

And make a suggestion to use interfaces that are in the `core` package.

Signed-off-by: moznion <moznion@gmail.com>
Also-by: Simon Bernard <sbernard@sierrawireless.com>

#933: Implement Destroyable, Startable and Stoppable for ObjectEnabler

To call each interface method on corresponded `LwM2mObjectTree` method.

Signed-off-by: moznion <moznion@gmail.com>

#933: Implement Destroyable, Startable and Stoppable for LwM2mObjectTree

And call each interface's method at related method of `LeshanClient`;
i.e.  `start()`, `stop()` and `destroy()`.

Signed-off-by: moznion <moznion@gmail.com>

#933: Add an interface `LwM2mClientObserver2` to handle unexpected error

This interface extends `LwM2mClientObserver` interface.
And make `LwM2mClientObserverAdapter` and
`LwM2mClientObserverDispatcher`
implement that new interface.
This doesn't break the backward compatibility because
`LwM2mClientObserver2` is compatible with `LwM2mClientObserver` and each
implementing class conceals the difference between `LwM2mClientObserver`
and `LwM2mClientObserver2`.

Signed-off-by: moznion <moznion@gmail.com>

#933: Call `onUnexpectedError()` when unexpected error occurred

If a task that are belong to `DefaultRegistrationEngine` raises
unexpected `RuntimeException` and the `observer` member variable
implements `LwM2mClientObserver2` (instead of `LwM2mClientObserver`),
it calls `LwM2mClientObserver2#onUnexpectedError()` hook.
The purpose of this hook gimmick is to shutdown the client application
mainly.

Signed-off-by: moznion <moznion@gmail.com>

#933: destroy LeshanClient on unexpected error.

Signed-off-by: moznion <moznion@gmail.com>
Also-by: Simon Bernard <sbernard@sierrawireless.com>