2.2.0: - Add: OpenMage 20.0.10 (by Christian Münch)

- Add: maintenance badge (by Christian Münch)
- Add: ext-simplexml for test-suite (by Tom Klingenberg)
- Add: makefile (by Tom Klingenberg)
- Add: missing changelog entry (by Christian Münch)
- Imp: Change autoloading from psr-0 to psr-4 (by Tom Klingenberg)
- Imp: Updated symfony dependencies (event-dispatcher, finder, process, validator, yaml) (Dependbot)
- Imp: Updated composer v1 dependencies (Dependbot)
- Imp: Updated php-cs-fixer dependency (Dependbot)
- Imp: Updated psy shell dependency (Dependbot)
- Fix: Fix-up message improvements (by Tom Klingenberg)
- Fix unnecessary assertions (by Tom Klingenberg)
- Fix static method invocations via '->' (by Tom Klingenberg)
- Fix missing assertion in config-test (by Tom Klingenberg)
- Fix missing debug output for user-config-file (by Tom Klingenberg)
- Fix namespace for composer init-command-test (by Tom Klingenberg)
- Fix clover.xml path (by Tom Klingenberg)
- Fix "$default-branch" macro use (by Tom Klingenberg)
- Del: unused import statements (by Tom Klingenberg)
- Del: superfluous @test annotations (by Tom Klingenberg)
- Del: deprecated string class (by Tom Klingenberg)
- Del: magerun magento2 entry-point (by Tom Klingenberg)