Fixed IDs in ICatalogBrowserPreferences
Added placeholder to application.tests plugin to fix project error
Changed the ITreeNode to be more like an intrusive collection (instead of the old composition based method), where each ITreeNode is also it's value (removed the getValue() method)
Fixed issue with persistence of the layer tree due to the change of ITreeNode to use Lists instead of arrays
Added *Child suffix to the ITreeNode add and remove methods