Plot for each run one black curve 'error vs. iterations' and aggregate the mean curve (red) and 
the median curve (green) of all runs. 
DIFFERENCE to multiRunPlot: 'error' is the distance of the ever-best feasible point 
in input space to the true solution solu.
multiRunPlot_2(
  dfAll,
  solu,
  fName = "multiRun",
  main = "",
  xlim = NULL,
  ylim = c(1e-05, 10000),
  ylog = TRUE,
  xlog = FALSE,
  target = 0.05,
  plotPDF = FALSE,
  subPDF = NULL,
  legendWhere = "topright",
  absErr = FALSE
)the data frame of all runs, obtained with multiCOBRA or loaded 
from .Rdata file
the true solution in input space of the problem (only for diagnostics).
["multiRun"] the name of the .Rdata file, printed as subtitle
[""] the name of the problem (e.g. "G01 problem"), printed as title
the x limits
the y limits
[TRUE] logarithmic y-axis
[FALSE] logarithmic x-axis
[0.05] a single run meets the target, if the final error is smaller than target
[FALSE] if TRUE, plot to <fName>.pdf
[NULL] optional subdirectory where .pdf should go
["topright"]
[FALSE] if TRUE, plot abs(error) instead of error.
z3, a vector containing for each run the ever-best feasible objective value
Print some diagnostic information: final median & mean error, percentage of runs which meet the
target (only if optim is available)).