Fixed Var Initialization Order

I simplified the field definition and initialization of the `Var` classes. With the old code, it was not possible to get the initial value when the log method `nodeCreated` has been called. With the new version, this is possible. This is due to the Scala initialization order. A [StackOverflow question](https://stackoverflow.com/questions/3830332/scala-initialization-behaviour) exemplifies the problem.