dsBoot = bootstrap(dataSet,nSamples)
    Bootstrap (sample with replacement) nSamples from the data
    set dataSet, and return the new data in dsBoot.
 
  [dsBoot,indices] = bootstrap(dataSet,nSamples) also returns
  the indices of the extracted data points in dataSet.
 
  [...] = bootstrap(dataSet,nSamples,p) sample from a
  non-uniform distribution specified by the nObservations x 1
  vector p.  p should "approximately" sum to 1, e.g.
     prtUtilApproxEqual(sum(p),1,eps(self.nObservations))
  Should return "true"