TAP plugin: enable detailed output for TAP with subtests

I use Jenkis TAP plugin to process output generated by Node.js modules.

There TAP subtest feature is used quite heavily. Unfortunately, TAP plugin does not provide detailed information on sub-tests and also does not include sub-test count in the total test number.

I have submitted a pull-request to fix this by introducing a new TAP plugin configuration option: https://github.com/jenkinsci/tap-plugin/pull/9

Going to attach an example data, where the "Flatten TAP output" feature has been used, to depict the effect on presented result.