SPARK-3883 SSL support for HttpServer and Akka

 - Introduced SSLOptions object
 - SSLOptions is created by SecurityManager
 - SSLOptions configures Akka and Jetty to use SSL
 - SSLOptions uses property file which is node-local to set SSL settings
 - Provided utility methods to determine the proper Akka protocol for Akka requests and to configure SSL socket factory for URL connections
 - Added tests cases for AkkaUtils, FileServer, SSLOptions and SecurityManager
The problem is that in standalone mode, Spark Master + Spark Workers play a role of the cluster manager. Launcher cannot talk to them without setting up SSL connection. Moreover, Spark Master cannot talk to Spark Workers without setting up SSL connection. 

I think that we are talking about two different things :)