Replace trait-implementing objects with classes

[beatngu13]

For instance, GuiStateMachineApi and its implementation look as follows:

trait GuiStateMachineApi { /* ... */ }

object GuiStateMachineApiImpl extends GuiStateMachineApi { /* ... */ }

Is this a thing in Scala to let objects implement traits? In Java, it looks a bit odd since I cannot code against the actual API anymore. Instead, I have to use the implementation directly:

Id stateMachineId = GuiStateMachineApiImpl.createStateMachine();
// ...

[tdauth]

Done. See cc01245