#6635 rename phpunit.xml to phpunit.xml.dist. did not know it is supported out of the box by phpunit

- renamed code coverage tests units to new structure
- removed processed system test files from git, added to .gitignore

we will deprecate old test classes in 4 months and not in 2, simplified test run by only allowing short version, added some examples

refs #5940 put tests in correct folders, better testsuite names, some tests still fail and I cannot figure out why