Add an --action option to select what to do

And add a reports_index option, in addition to the run_tests default
action.
Add tests descriptions
Replace tests definition hash by an array

Because the order we run the tests is important.
Add a page listing available tests
Rename tmpl/index.html to tmpl/testrun_report.html
Treat tor_bootstrap like a normal test
cleaning: remove the setup_tbb function
Fix general status on reports_index page
Add a report_format field in the report.yml file

This defines the version of the format used. This can be useful when
the format change in the future.
Store reports in a 'r' sub-directory

We may have other sub-directores later for other things than reports.