[multirhstest] allow access to measured timestamps in multirhstest
requested to merge lukas.renelt/dune-istl:feature/adapt-multirhstest-for-performancetests into master
This is useful e.g. to output the timestamps in whatever format you like, and to e.g. do some postprocessing before that (compute mean/variance, discard first timestamp as warm-up, etc).
Edited by Jö Fahlke