Test suites should work with vanilla phpunit

Example: One performance issue facing our test-suite is that it's single-threaded. There are a few ways to try to introduce threading, one of which is https://github.com/jlipps/paraunit . In theory, it should be a matter of downloading and running the "paraunit" command; however, the paraunit command assumes that we follow normal PHPUnit conventions (e.g. defining our customizations through phpunit.xml.dist and invoking tests by file-name or folder). But even if we just want to test the tool, we have do a fair bit of hacking.

Goal: Bring our test-suite in line with PHPUnit conventions so that it's easier to use other PHPUnit tools/documentation.

Details: I took a quick stab at it with https://gist.github.com/totten/45bdc573555d7cbb429c . I spot-checked by running some of the "api/v3" and "Civi" test-suits – although most cases passed, there were a number of regressions, so there's more to do (beyond the gist).