Fix doco
Add support for per-benchmark environments

This fixes gh-47 by making it possible to create inputs for benchmarks
on demand.
Supply a count of loop iterations to --only-run
Little bits of documentation
Refactor main so that --only-run is exclusive from analysis options
Eliminate some code duplication
Improve docs
Remove dead code

--HG--
extra : amend_source : 0919c25ae14e5fadedc920a0ae5672d593192a22