Short output summary

For calculations with large logic trees, thousands of outputs are generated, flooding the terminal. With this fix a compact version of the output summary is given, with at max 10 outputs per output_type. The full list can be
extracted with the options --lho and --lro, as before, so no functionality is lost. See the outputs of the demos in https://ci.openquake.org/job/zdevel_oq-engine/614/console to have an idea of how it looks like.