Update doxygen_dot_merge.pl

1) main() fn enumerator ## commented out for now
2) take care of icgraph and cgraph files passed as parameters together. This is done by looking for "dir=back" which would be set for icgraph files. In that case, we swap the nodes.
3) Generate the dot file @ html/merged.dot
4) generate the png and map files
5) generate a container html file that loads the png and map files.