Revise Risk demos

The goal of this pull request is to review risk demos (both hazard and risk part) in order to analyze possible performance problems. To this aim, I have added a README.txt in every risk demo folder. I have used the oats3 service to run the demos (on a standard laptop with 4 cores and 4Gb they have comparable ram/cpu consumptions).

The gist is that no demo takes more than one hour (Scenario Damage is the longest one and completes in about an hour) an no demo requires more than 250Mb of RAM per core.