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
There are a few options in SslContextFactory that are not covered here, such as:

- setAllowRenegotiate
- setNeedClientAuth
- setSslSessionCacheSize
- setSslSessionTimeout
- setTrustAll
- setValidateCerts
- setValidatePeerCerts
- setWantClientAuth

How hard would it be to have some sort of bypass from the configuration so that those who want to try these options can? I've done that in the past using BeanUtils, it's a little ugly but it mostly works.