Extract output into a dedicated class

[thekid]

See #13, this is the basis for being able to extract test run output.

Usage

The -r command line argument controls the used report:

# Default
$ xp test src/test/php/

# Explicitely setting report to `Grouped`, which is the default
$ xp test -r Grouped src/test/php/

# Using multiple reports (the `JSON` class is not part of this pull request!)
$ xp test -r Dots -r JSON,report.json src/test/php/

Change

CI now uses the compact Dots report as seen on the right-hand side.

[thekid]

Should we change the concept introduced here from output to report? See the following:

• https://github.com/dart-lang/test/blob/master/pkgs/test/doc/json_reporter.md
• https://mochajs.org/#reporters

[thekid]

Should accessing the file name be part of the https://github.com/xp-framework/reflection API?

[thekid]

Released in https://github.com/xp-framework/test/releases/tag/v1.4.0