DevKit updates

[ElectricMaxxx]

Let's start it here also

ToDo:

• fix tests
• increase phpunit version

[dbu]

thanks for keeping the dev-kit up to date. i commented on a bunch of things that i changed directly on this repo that should be ported into dev-kit rather than be reverted here.

[ElectricMaxxx]

Btw: no problems to start with a single repository and then roll it out to the other ones, but we are tightly coupled to our testing component in dev. So we have to do them both hand in hand.

[dbu]

cool! yeah lets drop old end-of-live symfony version.
i think we should up the minor version, as the strict types can reveal issues for users, and it will allow us to do a critical fix with symfony 2.8 support if really needed.

[ElectricMaxxx]

@dbu can you have a look at the tests, please? Do we expose an issue by using more strict code or did i break something through my changes?

[ElectricMaxxx]

@dbu nothing to do, my fault.

[ElectricMaxxx]

@dbu it took some time but now it is final and green. Any hints to add on changelog? any other issues?

[dbu]

great job! i only have some change requests for the changelog, otherwise this looks excellent now!