Many more updates to make the print_all_custom() routine work. Two new example

programs called "cell_statistics.cc" and "custom_output.cc" to demonstrate the
new features of the library. Command-line utility can do custom output now
also. Updated Doxyfile to 1.5.9. More documentation.


git-svn-id: https://code.lbl.gov/svn/voro/trunk@179 6221c96e-593b-4ce1-a500-64c4038a1943