KEGG KGML parsing and graphics with tests

(Single commit combined from Leighton's branch by Peter,
removing accidentally committed files and test output files)
Use standard online check in test_KGML_online.py

This avoids code duplication, but also is essential for
the run_tests.py --offline switch to work as intended.
Use system temp folder for downloaded file
Check for PIL in test_KGML_graphics.py
Use system temp folder for output files
Write sample PDF output from KGML to Graphics folder