A venn diagram of the list overlap structure for four lists. Each
region of the plot contains points representing each record in that list
intersection.
Arguments
overlap.counts
A vector of length 2^4 that gives the number of
records in each overlap in lexicographic order, i.e. 0000, 0001, 0010, 0011,
0100, etc.
main
the title of the graph
num.test.points
how many test points to generate as potentials to be
plotted in the circles.