Developer quick start: Document multiple applications

[markusjura]

So far the developer quick start only describes how to setup a Play 2.4 application. This guide should be enhanced to a Scala, Akka and Java application. For this we should use the code snippet tabs from the Play documentation: https://playframework.com/documentation/2.4.x/ThreadPools#Application-class-loader

[markusjura]

Also in the following developer sections we need to ensure that all application specific settings are covered:

• http://conductr.typesafe.com/docs/1.0.x/SignalingApplicationState
• http://conductr.typesafe.com/docs/1.0.x/ResolvingServices
• http://conductr.typesafe.com/docs/1.0.x/CreatingBundles
• http://conductr.typesafe.com/docs/1.0.x/DeployingBundles

[huntc]

We should also add support for compiling real code for use by the doc