add crit difference plot

[likunlan]

add crit difference plot
@alona-sydorova
#49

[alona-sydorova]

leider gibt es auf dem Plot keine critical differences. ich hab es mit createCritDifferencesPlot(mlr.benchmark.example, "measure.mmce.test.mean") wie in deinem Beispiel probiert

[alona-sydorova]

außerdem funktionieren andere Beispiele (large.benchmark und microbenchmark) gar nicht:

[likunlan]

@alona-sydorova
And now we can get a plot with baseline use test="bd"

the mlr::generateCritDifferencesData can not work with length(task.id) <2.
mircrobenchmark only has one task.id(we called problem), so my function also can not work.

the large.benchmark has many replication in a specificed problem. The input of mlr::generateCritDifferencesData do not consider about the replication. So, how to deal with these replication?