Plip 13260 step by step

We've completly updated the package, fixed some bugs and built a complete new teststructure to support two layer of tests, one for Dexterity and one for Archetypes. We have still 2 failing tests on dx, which are marked with skipTest for now, because we want to push Plone 5 forward and maybe someone who did the linkintegrity stuff initially can review that und has an idea why those tests fail.