Trialing plone.app.testing layers

- Since the current way (which is really legacy piling on each other) of
  doing testing is finally insufficient (i.e. lack of functional testing
  on a running test Zope instance over http in a managed manner), use of
  plone.app.testing and friends is now required.  However, at this point
  a monolithic setup is made for now, currently used by cellml.pmr2.  We
  will need to break up this thing later at some point to tidy this up.