users can install libtcl8.5 & libtk8.5 downstream if packages need these (or the dev versions thereof)

Appears that R reads only Rprofile.site but not an Rprofile file in
R_HOME/etc.  However, R installation creates a Renviron in R_HOME/etc,
not an Renviron.site.  It appears also that RStudio copies these into
/etc/R, and renames both with the .site suffix.  If they do not exist,
or /etc/R does not exist, it does not end up reading Renviron at all.
Pretty confusing to me...

makes more sense to fix the build date when the R version is also set.  Leads to removal of images older than R-3.1.1,
since MRAN does not exist during 3.1.0 (nor did docopt). This also makes sure littler and the install2.r script are
available at all levels.