Update Risk Event Based QA test

This pull request updates the test fixtures used for the risk event based QA test, following the changes in the hazard library. Furthermore, the number of stochastic event set has been set to 1000 (old value was 500) to lower to probability of test failures (we are not relying on the seed for checking the test results).

A small tool to extract gmvs from an hazard calculation and print them to standard output in csv format has been added. It is useful for passing ground motion values to alternative implementations (used to build the expected data).

Build status: http://ci.openquake.org/job/zdevel_oq-engine/99/