Add application base-class

[jakobod]

Implementing Application protocols currently requires a lot of boilerplate code that is identical across all application protocols. The stacking approach requires dispatching functions to the following layers even if the function is not needed for the application itself. This leads to a lot of code similar to:

void some_func(Args args) {
  next_layer_.some_func(args);
}

We should think about providing an application_base, that implements a default implementation for this. In the case that future applications require a different behaviour, these functions could simply be overridden.