Add an ABSReporting model
We need an ABSReporting model to store snapshot of the execution results
It would typically store scenario obtained for a given Goal (similar to old ResultStore)
It also needs some timestamp in order to be able to invalidate a given report if (for example) the model has changed.
for the moment: one ABSReporting file per source abs request (ie. its reach for goal in file A goes in A.ABSReporting