- Add org.eclipse.jdt.ui.prefs to fix svn:externel references.

- Update to tycho 0.21.0 to allow building with JavaSE-1.8.

refs 2352

- Re-add functionality to reload GenModel (i.e., to synchronize it with the ecore meta-model) when generating code (accidentally lost with last change)

   - This fixes the generation of code for derived generic classes, i.e. the generic parameter defined in the base class is correctly inserted into the Java code generated for the derived class.

- Validation of Ecore models before code generation is now enabled, and error markers are added to the problem view
   - org.fortiss.af3.fibex and org.fortiss.af3.refinement have been corrected accordingly 
   - (replaced platform:/resource with platform:/plugin references in ecore / genmodel files to ecore/genmodel files that do not reside in the workspace, but as a plugin in the Eclipse installation)
   - NOTE: Since the build on Jenkins does not run within an Eclipse instance, platform:/plugin references need to be patched to platform:/resource references in order to fix the lookup of Ecore meta-models usually shipped with Eclipse (e.g., Ecore.ecore), and that are manually copied into the buildroot on Jenkins.

- Change the semantics of the RemoveWarningsBuilder to remove warnings for all folders whose name start with one of the known prefixes (currently "generated-src"). Before, only warnings of folders precisely matching that name have been removed.
- This eliminates a lot of warnings from org.fortiss.af3.fibex/generated-src-fibex

- Update IDE dev tools plugin:
   - Prevent changes of plugin.xml and MANIFEST.MF.
   - While this avoid unwanted changes of these files (e.g.,
introduction of redundant dependencies), it also means that some
required modifications have to be performed manually now (in particular:
management of org.eclipse.emf.ecore.generated_package extension point)

- Date of IDE dev tools plugin has been bumped to date of first
implementation of this behavior (Aug 18, 2014).
Old version of plugin should be removed from Eclipse "dropins" directory.

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