Infrastructure for DeferredContentManager
Introduction of DeferredContentManager

DeferredContentManager is a pendant to TreeDeferredContentManager of the eclipse workbench bundle. However it supports deferred loading of children for arbitrary viewer implementation by the ViewerAdaper interface. Default implementations for tree and table are available with the first version.
Merge commit 'a3fc6fe0b7cfbcad7c7dbd9199250a77c88678f8' into development