These test classes were really testing SocketAppenderBase not
SocketAppender, per se.  The new implementation of SocketAppenderBase is
significantly different and will require a new unit test suite.

For consistency with logback-core.

For consistency with SocketAppender.

Convenience constructors that are used to set mutable fields that have
proper accessors add little value, and they make it more complicated to
subclass.  Best practice is to use constructor arguments only to
initialize fields that are immutable or for which an accessor method
cannot be safely provided within the design constraints of the class.

The only use of these constructors by logback modules is in the
SocketMin class.  However, because these constructors were exposed as
API (public modifier) there is a chance that other code is using them,
therefore marking them as deprecated rather than removing them.

The LoggingEventPreSerializationTransformer is completely stateless and
therefore inherently thread-safe.  Therefore, there is no reason to
create a distinct instance for each appender.  Moreover, once created it
never needs to be modified, therefore it should be properly marked as
immutable via the final keyword.

Introducing AbstractDiscriminator base class

add ResourceExistsPropertyDefiner

Fix for LOGBACK-230 - Support attribute "optional" in include element

fix logback-767

AppenderTracker is now extends AbstractComponentTracker, removed support for sifting in Gaffer, tests pass

 StatusListener has two instances OnConsoleStatusListener and instance by
 seted classname.
 The second be Judged that is ContextAware and LifeCycle's implement and start it.
 but The first is not to Judged.

 all StatusListener must be Judged and start it.