Update Oomph setup

Update Oomph setup

* Update API baseline to 4.8.0.201706111038-r
* Add second API baseline 4.7.1.201706071930-r for working on
  stable-4.8
* remove the "Modular Target"; re-use the target as defined in the
  EGit repository. We use TPD to define our target platforms; it
  makes no sense to define them again in the Oomph setup.
* add a step to import the projects into the workspace (was somehow
  missing for me using the Neon installer and our Egit.setup) Note
  that this must come _before_ the target platform setup, otherwise
  the target platform will not be known yet.

We might consider making Oomph also install TPD as it is needed to
work with our target platforms, and maybe Andrey's AnyEditTools,
which I personally always install; if only to get rid of trailing
whitespace in plugin.xml files automatically :-)

Tested by using the Neon Installer, "Eclipse IDE for Eclipse
Committers", then adding this file as "project" on the next screen
(green plus sign top right), then installing and launching a brand-new
Eclipse instance through the Installer.

Change-Id: I4f9ffa3216fde1ae415b7177b2a1eab3d8500bb8
Signed-off-by: Thomas Wolf <thomas.wolf@paranor.ch>