LOGBACK-818: add SSLSocketAppender and SimpleSSLSocketServer

This request provides an SSLSocketAppender and SimpleSSLSocketServer, supporting classes, and documentation updates.  Touch points with the existing code base:

- Extends SocketAppenderBase, overriding the getSocketFactory method.
- Provides new ch.qos.logback.core.net.ssl package containing classes used to support appender configuration
- Adds SSL types to the nested component types registry in -classic and -access
- Modifies SimpleSocketServer to allow startup to be reused for SimpleSSLSocketServer