Explore the 'declare result'. cf. #4
Read results from ancestors executions.

The initial type for ResultDescription was wrong and only allowed to
load from the executing scenarios whereas we want to read from the
already finished executions (i.e., the ancestors).
Prints consumed/produced results in the description.
Show dependencies in "describe".
Better names for the example (pong was before ping)
Declare which parameters to inherit when using the "consumes" function #4

Maybe we will revert the list of params from the one we inherit to the
one we "group-by" as it sounds more what we want to do.
The `consumes` function now ignore parameters.

The idea is that we should avoid mistakes as much as possible.
We now whitelist rather than blacklist parameters we want to inherit.