[SYSTEMDS-2641] Fix R slice finding baseline (doMC dependency)
[SYSTEMDS-2641] Fix R slice finding baseline (doMC dependency)

This patch fixes the R baseline script, by removing the doMC dependency.
Apparently, the CRAN doMC package is not available for windows. It can
be forced installed via

   install.packages("doMC", repos="http://R-Forge.R-project.org")

However, to avoid special cases in our automated install scripts, we
fallback to basic for loops instead. For performance comparisons, please
use the commented code with multi-threaded parfor loops for the main
slice evaluation loop.

apache/incubator-systemml,apache/incubator-systemml,apache/incubator-systemml,apache/incubator-systemml,apache/incubator-systemml,apache/incubator-systemml