As the Symphony\Yaml stuff disappeared with behat, we need another way
to load read the yaml files with database fixtures for the integration
tests.
As the php yaml extension is not distributed with PHP by default, this
creates it as another dev dependency!
Move unit tests to tests/unit/. Get the old still working UnitTests
into a working state again.
Updated composer.json with required-dev packages.
Create a new folder tests/acceptance for Behat functional/acceptance
testing. Add a first Feature draft of a Behat functional test for
local login.
