added classes that support creation/configuration of SSLContext

These are all supporting classes for the SSLSocketAppenderBase,
providing the ability to create and configure an SSLContext using
property values set in a Joran configuration file.
added SSLSocketAppenderBase to logback-core
added SSLSocketAppender to logback-classic
added SSL configuration types to DefaultNestedComponentRules
added SSLSocketAppender to logback-access
added SSL configuration types to the JoranConfigurator in access
modified SimpleSocketServer to allow startup logic to be reused
added SimpleSSLSocketServer to classic
added SSLSocketAppender documentation to the manual