add SslTlsSupport (ported from spray-io), see #3236

- also added TcpPipelineHandler for wrapping a pipeline
- added Java & Scala docs with a complete example
- test verify interop with standard blocking java SSL client and server
- test is placed in akka-remote to benefit from AkkaProvider for
  SecureRandom; should be moved into akka-actor eventually
add link to ticket from FIXME
Merge pull request #1351 from akka/wip-3236-SslTlsSupport-∂π

add SslTlsSupport (ported from spray-io), see #3236