Add option for disabling the legend on plots.
Use runtime paths for result files.
Remove now dead code.
Let user override error bar line width.
Update function names for consistency
Run an extra trial when first discarded

- Fixes bug where specifying 30 trials and discard first (default)
  gives an error due to only using 29 samples to calculate stats
Better error message for normalizing benchmarks
Support comparing individual benchmarks

- Previously could only compare groups of benchmarks
  where the elements of the groups had the same names as
  the elements of the other group.
Clean up Makefile a bit