testConnectionFails was expecting the connector thread to exit after
being interrupted, with latency no greater than the configured delay
between connection attempts.  However, the call to
SocketFactory.createSocket may not return immediately on interrupt.  

Now, we allow 4 * DELAY for the thread to exit. This commit should allow
more than enough tolerance, but (as it generally has no effect on the
run duration of the test) we could increase the allowed delay even
further if it proves too sensitive to timing variations on the build
system.

For consistency with SocketAppender...

Now the focus is on just describing the highlights and deferring
the details to the appropriate chapters of the manual.

Added some language to define "server component" and "client component",
fixed some overall formatting problems, lots of minor fixes and improvements,
added examples of using JSSE system properties, added standard footer.

These were previously in the appenders chapter, now moved to the
receivers chapter, and refined a bit to make them a bit easier to
follow.

Probably want to consider inserting the chapter on receivers
somewhere near the middle...

The Appenders chapter had become quite long due to the inclusion
of the documentation of Receiver components.

This branch refactors the previously contributed "server" and
"remote" components such that they now extend a common "receiver"
component.  A receiver is a component that receives logging
events from a remote appender.  A connection between and an
appender and a receiver may be initiated in either direction;
i.e. a receiver may initiate the connection to an appender or
vice-versa.  The receiver component is configured in Joran using
a <receiver> element.  The class specified in this element
determines whether the receiver will passively await connections
from remote appenders (i.e. as in the legacy SimpleSocketServer)
or whether it will initiate a connection to a remote appender
(a ServerSocketAppender).

Still needs lots of proofreading...

The subclass may need a reference to executor to pass to objects that
will need it later when the receiver is running.

This will make it easier to refactor SocketServer so that it extends
ReceiverBase.

The object that is composed with a ServerRunner already implements
LifeCycle.  Having a start method complicates the use of the runner
without adding any real value.

Also fixed up the taxonomy -- what was a SocketRemote is now a receiver
component that connects to a remote appender peer.

This will eliminate the need to add a nested component rule for each new
SSL component.

ReceiverAction can instantiate a component that is a subtype of
ReceiverBase.  SocketRemote and SocketServer will be refactored to
extend the ReceiverBase type.

The existing SocketRemote and SocketServer classes will be refactored to
descend from this base class.

In preparation for introducing the concept of a "receiver" component
(which can be either a component that listens passively for incoming
connections from remote peers or one that actively connects to a remote
peer), this commit fixes up the taxonomy in the ServerSocketAppenderBase
implementation.  Now a ServerSocketAppender will have zero or more
connected remote receiver clients.