YAML::Syck is much faster

This replace the report-dir option.

tbb_filename_infos is now called outside of test_tbb. This should allow
us to test other types of things.

This avoids checking the success status of each tbbfile to see if the
report had any error.

This defines the version of the format used. This can be useful when
the format change in the future.

And add a reports_index option, in addition to the run_tests default
action.

As this option will later be used for other things than files.

Also rename the 'results' hash from the report to 'tbbfiles', to avoid
confusion with the results from each tbbfile.