print_xfer fix, use defines, improve graph

dopple.cpp:
- fixed use of print_xfer_stats so that write_file_size isn't zero
- use defines for scale labels

dopple_script.py:
- added ability for graphing to figure out the scale and draw it as a
legend
- added output for total transfer & time per graph
- changed legend to use flag types instead of file name
- added dots when graph has fewer than 15 points
- added ability to clean up temporary log files
- added ability to check if app exists and run make to build if not